Anyone who has ever fought in MMA or wrestled will tell you that one of the most intimidating things you can go up against in competition is someone you know won't stop. From the initial bell to the end, they will keep coming at you full speed. And it is from that concept which the five best cardio freaks in MMA was born from. Notable MMA Title (s): UFC Heavyweight Title Fabricio Werdum is not simply just a black belt in Jiu Jitsu, he is one of the best grapplers in MMA. Any fighters watching his previous matches should know better than to go to the ground with Werdum. Barber had just started working more with vaunted striking coach Duke Roufus, and Ben Askren, one of the best pure wrestlers ever in MMA, has taken her under his wing. The torn ACL is a temporary.

There are prospects who flash their potential by conquering opponents in their own age bracket, and there are those who prove they can handle foes of greater experience and are ready to challenge the elite of their division. ESPN's second annual list of the top 25 MMA fighters under the age of 25 features prospects on the rise and those who already have established themselves.

There are UFC contenders and there are champions from various promotions. There are familiar names and newcomers.

The top two fighters from last year's list -- A.J. McKee and Sean O'Malley -- are too old to be eligible this year, but half of the top 10 returns.

ESPN's nine-person panel -- voters' names are listed below -- chose the prospects they view as possessing the most impressive combination of achievement and potential. Let the debates begin.

Marc Raimondi provides the breakdowns of the fighters.

1. Jimmy Crute (12-1)

UFC light heavyweight

Age: 24, turns 25 on March 4, 2021

Ranked No. 7 on ESPN's 25-under-25 list in 2019

The Aussie earned the top spot after landing performance-of-the-night bonuses for two wins this year. On Feb. 22, Crute faced Michal Oleksiejczuk, who was our No. 11 fighter under 25 last year. Crute slammed him to the mat and slapped a kimura on him for a first-round stoppage. He then landed a vicious right hand to the jaw of Modestas Bukauskas for a first-round KO on Oct. 17. UFC champions Israel Adesanya and Alexander Volkanovski make most of the MMA headlines out of Oceania, but Crute could be right there with them before long. The 6-foot-2 slugger is 4-1 in the UFC with finishes in all of his victories. The division is undergoing a facelift at the moment, and don't be surprised if Crute is a major player before long. He's laser-focused on fighting, to the point that he lives in his van parked in his gym's parking lot during training camps before fights.

2. Edmen Shahbazyan (11-1)

UFC middleweight

Age: 22, turns 25 on Nov. 20, 2022

Ranked No. 3 on ESPN's 25-under-25 list in 2019

Despite a Fight Night main-event loss to middleweight contender Derek Brunson in August, Shahbazyan has enjoyed more success than any prospect under 25. He started his UFC career in 2018 with four straight wins, three by KO/TKO. One of those was a dazzling finish of veteran Brad Tavares at UFC 244 in November 2019. Shahbazyan, the protégé of Ronda Rousey and her coach Edmond Tarverdyan, has an incredibly bright future as a 185-pound contender.

3. Song Yadong (16-4-1)

UFC men's bantamweight

Age: 22, turns 25 on Dec. 2, 2022

Ranked No. 8 on ESPN's 25-under-25 list in 2019

While Zhang Weili became the UFC's first Chinese-born champion last year in the strawweight division, Song is carving out his own path at bantamweight. And the path looks very good so far. The Team Alpha Male product is 5-0-1 in the UFC with a unanimous decision win over Marlon Vera in May, his most recent bout. While Song has been the beneficiary of some very close decisions, there's no doubting his place among the top prospects in the UFC.

4. Aaron Pico (7-3)

Bellator featherweight

Age: 24, turns 25 on Sept. 26, 2021

Ranked No. 13 on ESPN's 25-under-25 list in 2019

It feels as though Pico has been a 'prospect' in MMA for years -- and he has. Yet, the Californian just turned 24. Pico made a major change in 2019, moving to Albuquerque, New Mexico, to train at JacksonWink MMA, the home of former UFC champs such as Jon Jones and Holly Holm. After dropping his first bout with that team, Pico has won three straight in Bellator -- including a second-round KO Thursday night -- and is using the wrestling that nearly got him to the Olympics much more. The sky remains the limit for someone with Pico's prodigious talent and pedigree.

5. Brendan Allen (15-4)

UFC middleweight

Age: 24, turns 25 on Dec. 28

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Was not on this list last year

Perhaps Allen not being on this list last year was an oversight, but there's no denying the Roufusport product now. A blue-chip middleweight prospect, Allen has gone 3-1 in the UFC since October 2019 with finishes of very solid fighters in Kevin Holland and Tom Breese. Allen lost via second-round TKO to Sean Strickland on Saturday. Allen, a South Carolinian, is also the former LFA middleweight champion -- a belt he won when he was just 22 years old. Allen is a Brazilian jiu-jitsu black belt with eight submissions in 15 career wins. But he also has power and creativity on the feet. 'All In' will be a problem at 185 pounds for a long time.

6. Maycee Barber (8-1)

UFC strawweight/women's flyweight

Age: 22, turns 25 on May 18, 2023

Ranked No. 6 on ESPN's 25-under-25 list in 2019

Once one of the hottest prospects in all of MMA, Barber is currently sidelined following knee surgery, an injury she sustained in her first career loss, to Roxanne Modafferi at UFC 246 in January. Don't sleep on the Coloradan, though. Barber had just started working more with vaunted striking coach Duke Roufus, and Ben Askren, one of the best pure wrestlers ever in MMA, has taken her under his wing. The torn ACL is a temporary setback. Expect Barber to be back on a roll beginning in 2021.

7. James Gallagher (11-1)

Bellator bantamweight

Age: 24, turns 25 on Oct. 24, 2021

Ranked No. 9 on ESPN's 25-under-25 list in 2019

The protégé of Conor McGregor has won four in a row, three via submission finish. His 2018 loss to Ricky Bandejas seems like a lifetime ago. Now the challenge for Gallagher will be to defeat other contenders en route to a bantamweight title shot. The next year will be crucial for 'The Strabanimal' as he attempts to go from intriguing prospect with star potential to contender. Gallagher has a chance to be a real draw for Bellator in Europe, and the promotion is behind him. The time is now for a leap.

8. Arman Tsarukyan (15-2)

UFC lightweight

Age: 24, turns 25 onOct. 11, 2021

Ranked No. 25 on ESPN's 25-under-25 list in 2019

Tsarukyan had the unenviable task of fighting Islam Makhachev, one of Khabib Nurmagomedov's main training partners, in his UFC debut last year. The ethnic Armenian who trains out of Russia took Makhachev to the limit in a fight of the night loss. Since then? Tsarukyan has won two straight, over Olivier Aubin-Mercier and Davi Ramos, the latter a Brazilian jiu-jitsu dynamo. The former hockey player is poised to be a force in the UFC's extremely deep lightweight division.

9. Sabina Mazo (9-1)

UFC women's flyweight

Age: 23, turns 25 on March 25, 2022

Ranked No. 23 on ESPN's 25-under-25 list in 2019

Few have done more to improve their stock as a prospect over the past year than Mazo. Since August 2019, Mazo has won three straight and is coming off a third-round submission win over Justine Kish in September. Why was that so impressive? Mazo, from Colombia, is known more for her striking. The Kings MMA product is evolving her game and will be very problematic for her UFC women's flyweight peers in the stand-up department. Mazo also has power in both hands and a wicked head kick.

10. Umar Nurmagomedov (12-0)

UFC men's bantamweight

Age: 24, turns 25 on Jan. 3

Ranked No. 19 on ESPN's 25-under-25 list in 2019

The cousin of Khabib should have made his UFC debut at UFC 254 last month, but he withdrew because of an illness. Last year, Nurmagomedov picked up an impressive win in PFL and won the Gorilla Fighting bantamweight title in Uzbekistan. Look for the Dagestani prospect -- who is a striker, unlike his wrestling-focused older cousin -- to make plenty of waves in 2021.

11. Angela Lee (10-2)

One women's atomweight champion

Age: 24, turns 25 on July 8, 2021

RankedNo. 14 on ESPN's 25-under-25 list in 2019

In October, Lee announced that she was pregnant and would be out for a good portion of 2021. One Championship will allow Lee to keep her women's atomweight title and then defend it against the winner of an upcoming atomweight grand prix. There's no doubting that Lee is One's biggest female star and one of its biggest names overall. She had two losses in 2019 -- one up a weight class at strawweight -- but remains a force for the present and future once she returns.

12. Charles Jourdain (10-3-1)

UFC men's featherweight

Age: 24, turns 25 on Nov. 27

Was not on this list last year

While 2020 has been unkind to Jourdain in terms of decisions -- he has a split-decision loss and a rare split draw on his record -- the Canadian has impressed, especially in that close loss to Andre Fili and a TKO win over Dooho Choi last December. Before signing with the UFC, Jourdain was the featherweight champion and interim champion for Canada's TKO promotion. He's in a tough 145-pound division in the UFC and has already faced stiff competition. Let's see how he does with more experience moving into 2021.

13. Miranda Maverick (8-2)

UFC women's flyweight

Age: 23, turns 25 onJuly 21, 2022

Was not on this list last year

Other UFC women's flyweight fighters probably won't be too excited to see Maverick in the opposite corner. The former Invicta one-night tournament winner is athletic, strong and powerful. Maverick, from Virginia, won her UFC debut against Liana Jojua last month via TKO (doctor's stoppage) after opening up a nasty cut on Jojua's nose in the first round. Maverick has won four straight overall.

14. Kay Hansen (7-4)

UFC strawweight

Age: 21, turns 25 on Aug. 14, 2024

Was not on this list last year

Hansen is one of the first female fighters of the generation to become interested in MMA because of Ronda Rousey. Hansen was inspired by Rousey's knockout of Bethe Correia at UFC 190 in 2015 and started training from there. The Californian has a ton of potential, too, although her moment was halted -- at least temporarily -- by a unanimous-decision loss to Cory McKenna, who's also on this list. Hansen made her UFC debut in June, finishing former Invicta atomweight champion Jinh Yu Frey with an armbar submission. Sounds kind of like Rousey.

15. Christian Lee (14-3)

One lightweight champion

Age: 22, turns 25 on June 21, 2023

Ranked No. 22 on ESPN's 25-under-25 list in 2019

One Championship has featured Lee as an attraction for the past five years -- and he's still 22. Like his sister Angela, Lee is an MMA prodigy who grew up training in the sport in Hawai'i. 'The Warrior' has really come into his own lately. Since May 2019, Lee has won and defended the One lightweight title -- and won the One lightweight grand prix. He has five consecutive victories, four via finish, and his most recent loss was a disqualification due to an odd One rule banning suplexes.

16. Ismail Naurdiev (20-4)

Elite MMA Championship welterweight

Age: 24, turns 25 on Aug. 18, 2021

Ranked No. 15 on ESPN's 25-under-25 list in 2019

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'The Austrian Wonderboy' had a 2-2 run in the UFC and departed the promotion earlier this year. Naurdiev rebounded from some uneven performances by winning a tournament semifinal bout in the Elite MMA Championship promotion in Germany, defeating Tymoteusz Lopaczyk. At just 24, the Chechen-born welterweight is likely to make his way back to the UFC before long. He's too talented not to. Naurdiev already has 20 career wins in eight years as a pro.

17. Ilia Topuria (9-0)

UFC men's featherweight

Age: 23, turns 25 on Jan. 21, 2022

Was not on this list last year

The German-born featherweight seems like the real deal after an impressive win over Youssef Zalal, who is also on this list, at UFC Fight Night: Moraes vs. Sandhagen on Oct. 10. Topuria, who fights out of Spain, is a perfect 9-0 and has six finishes in his pro career. Before coming to the UFC, he was the Cage Warriors bantamweight champion. Winning a title in that United Kingdom promotion is usually a solid marker for future success on the biggest stage.

18. Usman Nurmagomedov (11-0)

Bellator lightweight

Was not on this list last year

Another cousin of current pound-for-pound king Khabib Nurmagomedov, Usman was signed by Bellator in October. Usman is 11-0 and trains with Khabib and his team at American Kickboxing Academy under coach Javier Mendez. Unlike his famous cousin, Usman is actually a striking specialist -- with excellent wrestling to boot. Ali Abdelaziz, who manages the Nurmagomedov clan in MMA, has said Usman is a 'better version' of Khabib. Scary.

19. Cory McKenna (6-1)

UFC strawweight

Age: 21, turns 25 on Nov. 7, 2024

Was not on this list last year

McKenna was a relative unknown as recently as three months ago, especially in the United States. But there's no downplaying what she has done. In August, the Wales native earned a contract into the UFC by beating Vanessa Demopoulos on Dana White's Contender Series. And on Saturday, she knocked off fellow under-25 standout Kay Hansen by unanimous decision. 'The Hobbit' is clearly making the most of her potential, training with UFC Hall of Famer Urijah Faber at Team Alpha Male in Sacramento, California.

20. Chase Hooper (9-1-1)

UFC men's featherweight

Age: 21, turns 25 on Sept. 23, 2024

Was not on this list last year

Hooper debuted in the UFC with a finish of David Teymur last December. He has since lost to Alex Caceres, his first pro defeat. But the Washington native is definitely one to watch, even on social media, where he has developed a following with self-effacing posts.

21. Youssef Zalal (10-3)

UFC men's featherweight

Age: 24, turns 25 on Sept. 4, 2021

Was not on this list last year

Zalal went 3-0 to start this year in the UFC before falling to Topuria last month. Zalal remains one of the top young names to watch in the lighter weight classes in the UFC. Training out of Factory X in Colorado under coach Marc Montoya, Zalal was a revelation earlier this year, winning twice during the pandemic -- and in exciting bouts. With his size -- 5-foot-10 -- and length, Zalal will be a tough out for other 145-pound fighters moving forward and will surely put on a show in the process.

22. Loma Lookboonmee (5-2)

UFC strawweight

Age: 24, turns 25 on Jan. 18

Was not on this list last year

The muay Thai veteran and first Thai-born fighter to compete in the UFC, Lookboonmee is 2-1 so far in the promotion, with a loss to strawweight contender Angela Hill on her record. Lookboonmee rebounded with perhaps the best performance of her career, a comprehensive unanimous decision win over former Invicta champ Jinh Yu Frey last month. With her striking skills, the Tiger Muay Thai product will be hard to handle at 115 pounds.

23. Luigi Vendramini (9-1)

UFC lightweight

Age: 24, turns 25 on Jan. 16

Was not on this list last year

'The Italian Stallion' returned to the UFC in September after two years away, knocking out Jessin Ayari in the first round. It was an incredible performance in his comeback fight after injuries. Vendramini, who hails from Brazil, has just one career loss, to dangerous UFC welterweight Elizeu Zaleski dos Santos. Back down at lightweight, Vendramini appears to be a tough out moving forward.

24. Joshua Pacio (19-3)

One flyweight champion

Age: 24, turns 25 on Jan. 10

Was not on this list last year

Flying under the radar a bit in One Championship, Pacio has put together a sterling résumé. Pacio, from the Philippines, is a two-time (and current) One flyweight champion, with two straight title defenses to his name. He has lost just once in the past three years, to former champion Yosuke Saruta, and he avenged that in 2019 to regain the belt. Pacio fights out of Team Lakay, which has been a stalwart for Asia's One promotion since its inception in 2011.

25. Sage Northcutt (11-3)

One welterweight

Age: 24, turns 25 on March 1, 2021

Ranked No. 24 on ESPN's 25-under-25 list in 2019

It's hard to believe Northcutt is still under 25, since he has been a fixture in the MMA world since being 'discovered' on Dana White's 'Lookin' for a Fight' show in 2015. Northcutt was considered an uber prospect at the time, and he started his UFC career with two straight finishes. The Texan went 6-2 in the UFC, but the promotion didn't re-sign him when he was a free agent in 2018. Northcutt signed with One Championship, and he broke several bones in his face in his 2019 debut, a knockout loss to Cosmo Alexandre. Northcutt has not fought since.

Panelists: Kel Dansby, Andrew Davis, Alisa Harrison, Ariel Helwani, Eric Jackman, Phil Murphy, Brett Okamoto, Marc Raimondi and Jeff Wagenheim