The loss is the ninth straight in Manhattan for Oklahoma dating back to 2013, but just their first loss to a team with a losing record this season.
“This group has done a great job of taking care of business, but unfortunately it may take this loss to make us better,” Oklahoma coach Lon Kruger said. “This conference is tough because if you don’t come to play every night, you’ll lose.”
Reaves scored 18 of his 25 points in the second half. De’Vion Harmon had 13 and Umoja Gibson had seven points and 11 rebounds (14-6, 9-5).
Late in the second half Reaves scored 10 straight points, but was the only Sooner to make a field goal in the final 10 minutes of the game. He sat the majority of the first half with two fouls - one was a technical.
Both teams shot 39% while Kansas State went 7 of 27 from 3 and the Sooners were 4 of 20.
Oklahoma: Other than Reaves, the Sooners went cold in the second half. This could be a major blow to postseason seedings.
Kansas State: This was the win that had been close for the Wildcats in the past two weeks. They are now 1-10 against top 25 teams this season.
Oklahoma hosts Oklahoma State on Saturday.
Kansas State travels to West Virginia on Saturday.