Before Saturday's career performance, Hartman had only averaged 14.1 minutes and 1.1 points per game.
“We couldn't lose this game,” Hartman said. “We're trying to make the (NCAA) tournament. We have to have better fight than they have.”
Between a Valentine's Day loss to Iowa State and Saturday, Oklahoma has lost four of its last six games entering Monday's regular-season finale.
If the Sooners (20-9 overall, 10-7 Big 12) win in Lubbock, they'll clinch the No. 3 seed for the Big 12 Tournament, which begins Friday in Dallas.
With the third seed, Oklahoma wouldn't meet national No. 1 Baylor until Monday's tournament title game.
“It's gonna help definitely,” Kornet said of the bench's improved play. “Especially against Baylor. I feel like we can beat them if we just go out there, make our shots and help any way possible. I believe in us.”