When Casey O’Neill announced in October 2020 that she signed with the UFC, hardcore MMA fans knew her ceiling was extremely high. The question was asked repeatedly though: How will the — at the time — 5-0 fighter fare against UFC competition?

O’Neill answered that question emphatically in her rookie year with the promotion.

“King” began her UFC tenure with a high-paced, suffocating second-round TKO victory over Shana Dobson, who’d previously pulled off a massive upset against another surging prospect in Mariya Agapova six months prior.

Four months later, the 24-year-old got her next step up in competition when she faced Lara Procópio at UFC Vegas 29. While the fight extended into the third round, O’Neill still showed out with a standing rear-naked choke submission that put her opponent out cold.

After back-to-back finishes to start her octagon run, O’Neill then was booked against Antonina Shevchenko — the older sister of the reigning and completely dominant UFC flyweight champion Valentina Shevchenko — and she made yet another statement. O’Neill took some shots from the striker in the early goings, but those familiar with the Xtreme Couture standout understood that she has no problem wading through the fire to assert herself in a fight. O’Neill bullied Shevchenko over the final stretch of the opening round before absolutely annihilating her opponent on the mat with brutal punches and elbows to cap off the biggest win of her career — and a memorable 3-0 2021 campaign.

We define Rookie of the Year as any fighter who graduated from the regional circuit to make their debut on a major show in a given year. And in 2021, O’Neill was the cream of the crop.

Next up, she’ll look to build upon that momentum in 2022 when she meets former title challenger and women’s MMA O.G. Roxanne Modafferi at UFC 271 in what will be the latter’s 50th and final professional fight. While O’Neill isn’t in any real rush to get to a title shot, another finish in her first pay-per-view bout could certainly set her up for a big opportunity later in the year.

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2. RAUSH MANFIO

With almost three years of inactivity in mixed martial arts, Raush Manfio lived one of the all-time sports cliches: When opportunity knocks, answer the door.

In Manfio’s case, on the other side of the door was $1 million and a Professional Fighters League championship.

A 2015 contestant on the fourth season of The Ultimate Fighter Brazil, Manfio hadn’t competed in an MMA bout since a June 2018 loss to Sidney Outlaw under the Titan FC banner. When Olivier Aubin-Mercier was forced out of the 2021 PFL season with an injury, Manfio stepped in as a replacement and earned three points with a split decision win over 42-fight veteran Joilton Lutterbach at PFL in April.

In June, Manfio was slated to be a replacement fighter once more, this time against his good friend: American Top Team training partner and then reigning lightweight champ Natan Schulte. But the fight didn’t take place, as Schulte was rebooked, while Manfio returned two weeks later to face former UFC champ Anthony Pettis at PFL 6. Again, Manfio came through on the other side via split decision.

Manfio earned his spot in the championship fight with a unanimous decision win against one of the great stories of the year in Clay Collard at August’s PFL 7 event to set up a chance for a true Cinderella story to take shape at the PFL championship event in October.

In one of the wildest fights of 2021, Manfio defeated Loik Radzhabov via unanimous decision to cap off a remarkable story — and one of the breakout campaigns in all of MMA in 2021 — while pocketing a cool $1 million in the process.

If there was a feel-good story of the year award to be given away, Raush Manfio would have to be in the conversation.

3. BRUNO SILVA

While the start to Bruno Silva’s UFC career was less than ideal, he came out of the gate in a big way when he finally made his octagon debut in 2021.

Silva was initially set to make his first promotional appearance against Deron Winn in June 2019 but was pulled from the bout and subsequently suspended for two years by the United States Anti-Doping Agency after testing positive for boldenone.

After spending 24 months on the sidelines, Silva took out his frustrations on a trio of UFC middleweights — beginning with Wellington Turman at June’s UFC Vegas 29 event, where Silva picked up his first UFC finish with a first-round TKO.

In his sophomore appearance, “Blindado” got to show that he’s not only a vicious finisher, but also quite resilient when he faced Andrew Sanchez at UFC Vegas 40 in October. Silva was down two rounds on one scorecard, while the others judges had it tied 19-19 following a wrestling-heavy attack from Sanchez that included a pair of nasty groin kicks in the opening round. Silva then took a third low blow — this time costing Sanchez a point — but it only woke up a monster, as Silva found his mark on Sanchez, smelled blood, and unloaded with a barrage of shots before the fight was stopped with a little over two minutes to go.

Silva capped off his year with an exclamation point and his second straight Performance of the Night bonus when he put away Jordan Wright in less than 90 seconds at UFC 269.

2022 will begin with an absolute banger for Silva as he is set to face Alex Pereira in March.

4. USMAN NURMAGOMEDOV

Bellator has spent the last two years bringing in some very high-level prospects, but few were more intriguing than Usman Nurmagomedov.

The 23-year-old has certainly lived up to the hype.

The cousin of former UFC lightweight king Khabib Nurmagomedov made his promotional debut at April’s Bellator 255 event and picked up a dominant unanimous decision win over a very game and durable Mike Hamel. It was a great first test for the super-prospect, one that Nurmagomedov passed with flying colors.

Since then, Nurmagomedov has spent a combined 7 minutes and 36 seconds in the cage with back-to-back first-round stoppages of Manny Muro and Patrik Pietilä to pick up finishes No. 11 and 12 over his impressive 14-fight winning streak to begin his professional career.

Where Nurmagomedov goes in 2022 is currently a bit of a mystery. While his in-cage work was tremendous, Nurmagomedov found himself in trouble with the law in November when he and a friend were arrested for allegedly running over a police officer at Kaspiysk Airport in Russia.

If he is able to get his legal troubles behind him, Nurmagomedov will be a very interesting player to watch in the Bellator lightweight division.

5. MANON FIOROT

The UFC women’s flyweight division will be intriguing to watch over the next couple of years — not just because of our Rookie of the Year winner, but also due to a slew of emerging contenders, which has to include Manon Fiorot.

Fiorot signed with the UFC to replace an injured Natalia Silva against Victora Leonardo at January’s UFC Fight Island 8 event. The former UAE Warriors flyweight champion certainly didn’t disappoint, steamrolling over a very tough Leonardo en route to a second-round standing TKO.

The result was the same in her follow-up performance against previously undefeated Tabatha Ricci. Again, Fiorot used her incredible striking to hurt and unload on Ricci to pick up her fifth straight finish.

A step up in competition for Fiorot was desired for MMA fans — and that’s what they got at UFC Vegas 40 when she faced Mayra Bueno Silva. Fiorot once again showcased her superior striking while mixing in some takedowns. Fiorot swept the scorecards, even earning a 30-26 in handing Silva just her second career loss.

Fiorot will begin her 2022 in a big fight against former title challenger Jessica Eye at UFC 272 in March. With a win, the 31-year-old will certainly take a leap forward in the title contender conversation.

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Here is how the voting for MMA Fighting’s 2021 Rookie of the Year played out.

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