Kansas State coach Bill Snyder declined to discuss the nature or severity of it afterward, and said he wasn't sure whether Klein would be available for next Saturday's game at TCU.
"Obviously he was injured or we wouldn't have taken him out," Snyder said.
Klein scored his 50th career rushing touchdown on a quarterback sneak early in the third quarter to give the Wildcats (No. 2 BCS, No. 3 AP) a 38-17 lead. The Heisman Trophy frontrunner didn't come out for their next offensive series and was seen talking to a trainer on the sideline.
Klein was 16 of 22 for 245 yards and had 17 carries for 65 yards when he left the game. Daniel Sams entered as his replacement.
Information from The Associated Press was used in this report.