5 champions from rival promotions who won big in their UFC debuts

This weekend will see former Bellator two-division champion Patricio Pitbull make his UFC debut against Yair Rodriguez. The Brazilian will no doubt be desperate to win big in his first bout in the octagon.

If Patricio Pitbull can win this weekend, he'll join a surprisingly short list of champions from rival promotions who won big in their debut fight in the UFC.

Often, added pressure and 'octagon shock' are blamed for the failure of rival champions in their debuts, but this wasn't the case with the following fighters.

So prior to Patricio Pitbull's arrival, here are five champions from rival promotions who secured monumental victories in their UFC debuts.

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#5. Michael Chandler vs. Dan Hooker - UFC 257

A three-time lightweight champion in Bellator MMA, Michael Chandler arrived in the UFC in early 2021. Coincidentally, he didn't arrive as the reigning Bellator champ, having lost his crown to none other than Patricio Pitbull in 2019.

Despite that loss, fans had dreamed of seeing 'Iron' in the octagon for years, thanks to his high-octane style built around his powerful punching and wrestling games.

Matched with tough veteran Dan Hooker in his debut fight, it didn't take long for the former Bellator champ to make his mark.

Midway through the first round, Chandler dropped 'The Hangman' with a leaping left hook, and wasted no time in finishing him off on the ground. Given the renowned toughness of Hooker, the outcome was shocking and turned Chandler into an instant star.

In the years that have followed, Chandler has remained a poster boy of the UFC despite having a 2-4 win-loss record.

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#4. Ben Askren vs. Robbie Lawler - UFC 235

While it's fair to say that his time with the UFC didn't pan out as he'd have liked it to, it's impossible to deny how exciting Ben Askren's octagon debut was.

The former Bellator and ONE Championship welterweight titleholder arrived in the promotion in 2019 after being "traded" with former UFC flyweight champ Demetrious Johnson heading to ONE in exchange.

Given his reputation as somewhat of a one-dimensional grappler, nobody was quite sure what to expect from 'Funky' in his debut fight against former 170-pound kingpin Robbie Lawler.

What they perhaps didn't expect was one of the wildest fights of the year.

In trademark fashion, Askren shot for a takedown in the opening seconds, only for 'Ruthless' to block and slam him violently to the ground. From there, Lawler hammered at the former Bellator champ, busting him open and coming close to a finish.

Somehow, Askren survived, and it didn't take him long to turn the tables. He managed to take Lawler down, and in a scramble, got his back and secured a bulldog choke. Moments later, Lawler apparently passed out, ending the fight in favor of Askren.

It looked like the best possible start to Askren's octagon career, but in the end, he lost his next two fights and headed right into retirement. Despite that, this remains one of the most thrilling debuts from a rival champion in UFC history.

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#3. Justin Gaethje vs. Michael Johnson - TUF 25 Finale

When Justin Gaethje arrived in the UFC back in 2017, he was the reigning WSOF lightweight champion, a title he'd held since 2014.

'The Highlight' also held the reputation as one of MMA's most exciting fighters, and he was able to live up to that reputation in a thrilling octagon debut.

Matched with veteran striker Michael Johnson in the headline bout of the TUF 25 Finale, Gaethje didn't need long to settle into his new surroundings.

He quickly began to attack 'The Menace' with his trademark combinations and booming leg kicks, and also showed off his renowned chin, taking some serious shots in return.

By the second round, despite the grueling pace, Gaethje was still ready to push on, while Johnson was visibly wilting. Unsurprisingly, 'The Highlight' kept on pushing forward and eventually, a violent combination left Johnson slumped in a heap.

It was a dramatic debut for Gaethje in one of 2017's best fights, and he's gone onto massive success since, winning both the interim lightweight title and the 'BMF' title. Overall, he's one of the most successful rival champions in octagon history.

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#2. Kayla Harrison vs. Holly Holm - UFC 300

This June is set to see two-time judo Olympic gold medalist Kayla Harrison challenge for the bantamweight title, as she will take on reigning champ Julianna Pena.

If Harrison can pull the win off, it'll be the biggest achievement of her MMA career to date, but it won't be her first title win. The Olympian claimed two PFL titles in the lightweight division before moving to the UFC in 2024.

It's fair to say that Harrison's octagon debut was definitely one of the most impressive of any rival champion in the promotion's history, too.

Faced with former bantamweight champ Holly Holm, there were questions not only over whether Harrison could compete at the very top level, but also whether she could make the 135-pound limit in the first place.

The former PFL champ easily cleared the weight hurdle, though, and quickly set to clearing the second. She took Holm down with ease in the first round and beat the hell out of her, before repeating the trick in the second.

Eventually, Harrison secured a fight-ending rear naked choke, becoming just the second fighter to submit 'The Preacher's Daughter' in her MMA career.

To label the performance flawless would be an understatement, and if Harrison can go onto dethrone Pena, she'll likely be recognized as an all-time great.

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#1. Alistair Overeem vs. Brock Lesnar - UFC 141

It's arguable that the most dominant UFC debut from a champion of a rival promotion came in 2011, when Alistair Overeem destroyed former heavyweight champ Brock Lesnar in a single round.

While he'd been stripped of his title due to a contract dispute a couple of months prior, Overeem was widely recognised as the Strikeforce heavyweight champion.

His octagon debut was hugely hyped up, as the former 205-pounder had reinvented himself as a hulking heavyweight, claiming titles in DREAM and K-1 as well as Strikeforce.

Nobody was really sure how he'd deal with the powerful wrestling of Lesnar, though, but fans of 'The Demolition Man' need not have worried.

Lesnar wasn't even able to land a single takedown as Overeem used his brutal striking to assault the former WWE champion's body with knees and kicks.

Eventually, a big left kick to the liver caused Lesnar to double over, and Overeem wasted no time in finishing him off. The beating was so bad that Lesnar headed directly into retirement afterwards.

Overeem never managed to claim UFC gold, losing out on an opportunity after a positive drug test and then falling to Stipe Miocic in his challenge in 2016. However, this debut still stands up as one of the most memorable in octagon history, well over a decade on.