Shai Gilgeous-Alexander scored 15 of his 35 points in the fourth quarter as the Oklahoma City Thunder rallied for a gritty 111-104 victory over the Indiana Pacers that leveled the NBA Finals at two games apiece on Friday.

Frustrated for much of the game by Indiana's relentless defense, NBA Most Valuable Player Gilgeous-Alexander found a way to fight through.

He followed a three-pointer with a pull-up jumper to give the Thunder their first lead since the first half with 2:23 remaining.

They wouldn't trail again. Gilgeous-Alexander, who didn't get to the free-throw line in the first half, added six free-throws in the final 44 seconds.

"It's a dog fight," Gilgeous-Alexander said after another intense, physical battle between the two teams. "Every time you step on the floor, on both ends of the floor they make you work."

Jalen Williams scored 27 points, Chet Holmgren added 14 points and 15 rebounds and Alex Caruso chipped in with 20 points off the bench for the Thunder.

Pascal Siakam scored 20 points to lead Indiana, adding eight rebounds, five assists and five steals.

Tyrese Haliburton scored 18 points, Obi Toppin added 17 off the bench and the Pacers led by 10 late in the third quarter.

But Oklahoma City -- who dropped back-to-back games just twice this season and haven't lost consecutive games in the playoffs -- clamped down defensively in the fourth, determined not to fall in a 3-1 hole.

"We knew it when we woke up this morning -- 3-1 is a lot different than 2-2 going back home," Gilgeous-Alexander said. "We played with desperation to the end the game and that's why we won."

Gilgeous-Alexander said the Thunder must "maintain the same desperation" when they host game five on Monday.

The Thunder are seeking their first title since the franchise relocated to Oklahoma City in 2008, having won it all in 1979 as the Seattle SuperSonics.

The Pacers, chasing their first NBA title, struck first in another fast-paced opening quarter in front of their energized fans, making four of their first five shots and building a nine-point lead midway through the opening period.

Oklahoma hit back, putting together a 9-0 run to tie it, but the Pacers -- with a strong defensive effort on Gilgeous-Alexander and four steals from Pascal Siakam -- emerged from the first period with a 35-34 lead.

The back and forth battle continued in the second, when Oklahoma City led by as many as six but could never pull away and Haliburton converted a three-point play -- driving through traffic for a layup and making the free throw, his first of the series -- to put Indiana up 60-57 at halftime.

By then, tensions had already ratcheted up. Toppin was assessed a flagrant foul for a check that sent Alex Caruso sprawling under the basket.

Thunder center Isaiah Hartenstein confronted Toppin and both received technical fouls.

- 'Unreal' Gilgeous-Alexander -

OKlahoma City's Luguentz Dort was later assessed a flagrant foul for swiping an arm over Toppin's head.

Toppin gave Indiana the first double-digit lead of the game with a dunk that put them up 86-76 late in the third.

But the Thunder dug deep, tying it up four times in the fourth quarter before Gilgeous-Alexander came through.

"You're up seven at home you've got to dig in and find a way and we were not able to do it tonight," Pacers coach Rick Carlisle said. "But give them credit. They kept attacking, kept attacking, and their defense was great down the stretch."

Oklahoma City closed the game on a 12-1 scoring run, and Gilgeous-Alexander was the driving force.

"He's unreal," Thunder coach Mark Daigneault said, although Caruso said nothing Gilgeous-Alexander does surprises him anymore.

"I've seen him do it night after night," Caruso said. "He doesn't show a lot of emotion on the court, but he's one of the most competitive guys in this league."