CHICAGO – After an exhausting 15 minutes that seemed to have both fighters gassed early in the second, Blagoy Ivanov walked away with a unanimous decision.

Ivanov (18-2 MMA, 2-1 UFC) outworked Tai Tuivasa (8-2 MMA, 3-2 UFC) with a pair of 30-27 scores and a 29-28 from the judges in a fight that featured plenty of slugging, but also plenty of tired clinching.

The heavyweight bout opened up the main card of Saturday’s UFC 238 event at United Center in Chicago. It aired on pay-per-view following prelims on ESPN and UFC Fight Pass/ESPN+.

Tuivasa went to the center of the cage to look for an opening, but Ivanov threw the first punch 40 seconds in. Tuivasa immediately countered with a low kick, then backed Ivanov up with a quick rush. A stiff right hand connected for Tuivasa, and it forced Ivanov to clinch up 75 seconds into the round. Tuivasa pushed him to the fence, landed an elbow and stayed heavy.

They broke apart at the midway point of the round and Tuivasa nearly landed a spinning elbow. But seconds later, Ivanov clipped Tuivasa and sent him crashing to the canvas. Ivanov rushed in, but couldn’t put Tuivasa away. They tied up, which gave Tuivasa time to recover. With 90 seconds left, they traded big bombs, then locked up once more. It was a firefight down the stretch, but neither landed big enough to put the other in trouble.

A minute into the second, Tuivasa looked like he found his range again and put Ivanov in trouble with big punches and elbows. But after another tie-up, Ivanov still was in it, though both big men looked like their gas tanks were running on empty with a full potential eight minutes left. Ivanov pushed Tuivasa forward, but couldn’t connect cleanly midway through the frame.

Tuivasa put a two-punch combo on Ivanov, then kicked his leg. But seconds later, Ivanov landed crisp jabs that sent the sweat flying off Tuivasa’s head. A standing elbow followed a moment later. Ivanov had a late guillotine choke attempt that he released fairly late after the bell, but they went to the third.

Tuivasa nearly kicked Ivanov’s lead leg out from under him twice in the opening 30 seconds before Ivanov tied him up on the fence. Ivanov landed what appeared to be a low knee, but referee Dan Miragliotta didn’t stop things. And moments later, Ivanov again went after a standing guillotine choke. He couldn’t hold it, though, and they resumed an exhausted clinch game. They traded positions on the fence and Ivanov kept after the choke, but never could hold it.

Up-to-the-minute UFC 238 results include:

• Blagoy Ivanov def. Tai Tuivasa via unanimous decision (29-28, 30-27, 30-27)
• Tatiana Suarez def. Nina Ansaroff via unanimous decision (29-28, 29-28, 29-28)
• Aljamain Sterling def. Pedro Munhoz via unanimous decision (30-27, 30-27, 30-27)
• Alexa Grasso def. Karolina Kowalkiewicz via unanimous decision (30-27, 30-27, 30-27)
• Calvin Kattar def. Ricardo Lamas via TKO (punches) – Round 1, 4:06
• Yan Xiaonan def. Angela Hill via unanimous decision (29-28, 29-28, 29-28)
• Darren Stewart def. Bevon Lewis via unanimous decision (29-28, 29-28, 30-27)
• Eddie Wineland def. Grigorii Popov via knockout (punches) – Round 2, 4:47
• Katlyn Chookagian def. Joanne Calderwood via unanimous decision (30-27, 29-28, 29-28)

For complete coverage of UFC 238, check out the UFC Events section of the site.