In beating Robert Whittaker for a second time, Israel Adesanya is running out of worlds to conquer, while condemning the Australian to title purgatory.

In their title rematch at UFC 271 in Houston, Adesanya's technical skill, ability to control the distance and excellent takedown defence helped him navigate the challenge of Whittaker and retain the belt he claimed back in 2019.

The sequel could not have been more different to the original. Gone were the kamikaze blitzes that Adesanya exploited to finish Whittaker in Melbourne – this was a far more cerebral battle, with both fighters searching constantly for the tiniest of openings.

In the end, Adesanya's range helped him keep Whittaker off him and his precision as a striker was once again on show. Unless he moves up to light-heavyweight again, he is MMA's unsolvable puzzle, a riddle without an answer, a maze with no exits and no prize in the centre.

With Whittaker out of the picture, Adesanya could well put together a lengthy streak of title defences. Simply put, he is running out of challengers who have a realistic chance of beating him.

"I knew he was going to bring everything cause last time I took everything away from him," Adesanya said.

"So he had nothing to lose. Like I said, I'm the champ, you want it, come get it."

Jared Cannonier was impressive in his second-round victory over Derek Brunson on the undercard, and will likely fight for the title next, but for all the American's power and panache, Adesanya will be warmly favoured. Beyond that, the talent pool runs thin.

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Adesanya has said he's chasing the old gods of the UFC, the likes of Georges St-Pierre and Anderson Silva, who put together title reigns that lasted over half a decade. He has that chance before him, because if Whittaker can't get the job done it's difficult to imagine who can.

Whittaker was game and fought well. If he had been awarded the decision it would have been controversial but far from a robbery. He is clearly the second-best middleweight in the world, but it's hard to have a rivalry when only one side wins. And as close as this fight was, it wasn't quite close enough to justify a third meeting.

Whittaker will exist in a unique realm for the foreseeable future — he said in the lead-up how much he enjoyed the process of climbing the ranks again, but now he's trapped in the netherworld between title contention and the rest of the division.

There is not a middleweight in the world who would be favoured to beat him, except for Adesanya. Much like Max Holloway and Alex Volkanovski at featherweight, there are two genuine championship-calibre fighters but only one belt between them.

"I know I started off rocky in that first round but I feel like I took every round after that," Whittaker said after the fight.

"What do they say? Don't leave it to the judges. I'm happy that I fought my heart out. I'm gutted. I thought I did enough. I thought I took that.

"I was surprised with the decision. It is what it is. I'm not going to take anything away from him. He's the champ. He beat me for the second time. We're the two best in the world, I know this, he knows this. We know this."

Earlier, Tai Tuivasa produced the best performance of his career to knock out Derrick Lewis in the second round and cement his status as a top contender at heavyweight.

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In a bout that lived up to the high expectations, Lewis was in control after a strong first round, only for Tuivasa to turn the tables and put the Houston native to sleep with a fearsome elbow strike.

It sets up the possibility of Tuivasa facing heavyweight champion Francis Ngannou in what would be one of the biggest fights in Australian mixed martial arts history.

It's been a meteoric rise for Tuivasa, who had lost three straight fights before ripping off his recent five-bout winning streak, but the fighting pride of Western Sydney has risen to every challenge he's faced since.

While there was plenty of blood and bone, as Tuivasa promised, he also stayed cool under fire when Lewis brought the heavy pressure in the first round.

What has changed in Tuivasa recently is his willingness to be patient and wait for opportunities to present themselves, then unleashing the torrent of violence that comes so naturally to him.

He is a far more controlled fighter than his Wildman reputation indicates, and the images of the towering Lewis collapsing face-first on the canvas have shown the world what Tuivasa already knew – he can knock out any man in the world, and if he ever takes the title back to Mt Druitt they'll run out of beer and shoes in quick time.

Flyweight Casey O'Neill did her own title chances a world of good with a dominant victory over American veteran Roxanne Modafferi.

O'Neill has now won four straight since her UFC debut early last year and impressed with her volume striking and work rate in a strong performance.

The Gold Coast slugger could potentially be only one more win away from facing champion Valentina Shevchenko.