He's played in the most big games on this team.
He's one of if not the best competitor in the NBA night in and night out," Gilgeous-Alexander said.
Gilgeous-Alexander also credited the team's identity. "We just played to who we were tonight," he said.
"We definitely got better from the last game."
Oklahoma City took control with 40 points in the second quarter.
San Antonio cut a 20-point deficit to eight in the third quarter, but frustrations grew over uncalled goaltending and out-of-bounds plays.
Spurs coach Mitch Johnson said of an ignored challenge that led to his technical foul: "They just said they didn't see me."
Stephon Castle led San Antonio with 24 points. Julian Champagnie added 22, and Victor Wembanyama scored 20.
The Spurs missed 29 of 41 three-point attempts.
"To beat a team of this calibre, in their building, with the stakes, we'll need to be a lot better to give yourself a chance," Johnson said.
Game 6 is scheduled for Thursday in San Antonio.
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The series winner will face the New York Knicks in Game 1 of the NBA Finals on June 3.
