CHICAGO — Robert Whittaker barely got the fight to the judges before they handed him a win in a grueling rematch.

Whittaker survived a staggering blow in the fifth round to beat Yoel Romero in a split decision at UFC 225 on Saturday night.

Whittaker (21-4) won despite being outworked in the fifth. He was shaken up after taking a hard left hand from Romero (13-3) early in the round, and the fight was scored 48-47 by all three judges, one in Romero's favour.

Whittaker also injured his right hand in the first round.

"Yoel hits like a truck and I just had to try and survive and make the comeback," Whittaker said. "I could have seen it going any way because it was tight, but I hit him a lot and I thought I did enough to get three of the five rounds. It was a really tough fight but I want to go back and talk to my team and see what we think should be next."

The fight was in jeopardy when Romero missed weight at 185 pounds Friday morning. Romero was one pound over in the first weigh-in, then .2 over in the second and final weigh-in. The fight was originally for the middleweight championship. The duo fought anyway, but without a belt on the line.

"It's a long flight to Chicago. If I travel 22 hours, I'm fighting someone, mate," said Whittaker, who is from New Zealand.

Romero was tentative in the first round, and Whittaker damaged his right eye in the second with a kick. Romero then exploded in the third, landing a left and bringing down the champ. Romero controlled the third round with a series of combinations, but Whittaker was able to land two significant kicks.

Whittaker kicked Romero below the belt in the fourth round, which put a halt to the fight for about a minute. Whittaker regained control in the fourth, but Romero landed a hard left and right late in the round. In the fifth, Romero controlled the round, bring down Whittaker with a series of left hands, then pounded with a right hand.

At UFC 213, Whittaker gutted out a grueling 25-minute brawl against Romero with all three judges scoring it 48-47.

This card featured five current and former UFC champions in front of a sold-out United Center crowd. In the co-main event, Colby Covington (14-1) defeated Rafael dos Anjos (28-10) for the interim welterweight championship in a unanimous decision. Covington controlled the five-round title fight by outstriking the former lightweight champ.

The outspoken Covington called out current welterweight champ Tyron Woodley. Woodley has been out indefinitely with a shoulder injury.

"This moment is exactly what I dreamed of," Covington said. "This is what I've been saying all week, to all the media, to all the fans. This is my moment and nobody can say anything about it. I'm the new money fight in UFC. Tell Tyron Woodley that his time is up. This is the real belt."

In his second pro fight, former WWE star CM Punk, a Chicago native, had the crowd chanting his name in the first round, but Punk was unable to show any sense of force in the cage against Mike Jackson (1-1). Jackson peppered Punk (0-2) with punches to the face throughout the fight and won in a lacklustre unanimous decision. Punk, who was featured on the main card, didn't help his standing with the UFC after two disappointing showings.

Another Chicago native, Curtis Blaydes, kept climbing the heavyweight rankings with an impressive second-round TKO of Alistair Overeem. Blaydes (10-1-1) dropped Overeem (43-17-1), then damaged the No. 2 contender's face with a series of elbows before the fight was stopped.

Former heavyweight champ Andrei Arlovski (27-16) lost in a slugfest to Tai Tuivasa (10-0). All three judges scored it 29-28. Holly Holm (12-4), former bantamweight champ, was impressive with her pound and ground game beating Megan Anderson (8-3) in a unanimous decision.

In a flyweight fight, Sergio Pettis (17-3) defeated No. 1 contender Joseph Benavidez (25-5) in a split decision. Pettis' striking game was the difference as he bounced back from a unanimous decision loss to No. 2 contender Henry Cejudo.

Former lightweight champ Rashad Evans took a right knee to the face, followed by a right hand by Anthony Smith (29-13) before the fight was stopped in the first round as Evans (24-8-1) lost his fifth straight fight.

During the card, the UFC announced former UFC bantamweight champ Ronda Rousey will be inducted into the UFC Hall of Fame on July 5 in Las Vegas. Rousey was the first female fighter signed by the UFC and had six consecutive title defences.