STILLWATER, Okla. (AP) -- Kansas coach Bill Self soon will learn whether his team has the toughness he wants to see.
Freshman Jawun Evans had 22 points, eight assists and six rebounds to help Oklahoma State upset the third-ranked Jayhawks 86-67 on Tuesday night.
Frank Mason III scored 14 points and Perry Ellis added 13 for Kansas (15-3, 4-2), which has lost two of its past three to fall out of a tie for the Big 12 lead.
"I've always questioned whether or not this team was tough enough from a mental standpoint to fight through some stuff, and to be honest with you, we haven't shown that we are," Self said. "But we're not going to go anywhere if we don't show that we are, so this is probably, if there's any positive out of this -- we'll find out who we really are. I know we're capable of being much better than this."
Jeff Newberry scored 13 points and Jeffrey Carroll added 11 for the Cowboys, who had lost four straight. Oklahoma State shot 50 percent from the field, made 11 of 21 3-point attempts and outrebounded the Jayhawks 38-31.
"We're so spoiled here, we haven't had many games like this over the years, but we've had them," Self said. "Mature guys understand it's one game and bounce back, but it is disheartening at the moment."
Oklahoma State (10-8, 2-4) made 23 of 26 free throws while Kansas made just 13 of 24 as the Cowboys beat Kansas in Stillwater for the third straight time and the fifth in seven years.
"I think about everything that could go wrong with us went wrong," Self said. "We didn't make shots when the game was at least somewhat in balance, and they were so athletic, and of course, they played great. They made timely shots, had seven different guys make shots. What went wrong was they were far better than us."
Oklahoma State showed it might compete early. Carroll stole the ball, then hit a 3-pointer to give Oklahoma State an 18-13 lead midway through the first half. Kansas battled back to take the lead, but Carroll later hit 3-pointers on consecutive possessions, both on assists from Evans, to give the Cowboys a 40-38 lead. Evans hit a 3-pointer on the following possession, and Oklahoma State led 43-38 at halftime.
The Cowboys made 7 of 13 3-point attempts in the first half and shot 50 percent overall.
Oklahoma State extended its lead to 50-43 early in the second half, and a two-handed baseline jam by Newberry pushed the lead to 10. A 3-pointer by Tavarius Shine gave Oklahoma State a 66-55 edge with about 8 minutes remaining. Another 3 by Shine made it 71-57.
Like coach always says, if you're not making shots, you have to get stops, and they were making shots and we couldn't get stops," Ellis said.
Kansas: G Brannen Greene sat out with a bruised left knee. He averages 7.2 points per game and shoots 58 percent from 3-point range. ... Cheick Diallo got his first start for Kansas in place of Hunter Mickelson. ... Oklahoma State fans gave Kansas play-by-play radio voice Bob Davis a standing ovation. He is retiring after this season.
Oklahoma State: The Cowboys beat the Jayhawks in consecutive meetings for the first time since 2000. ... Evans scored 42 points last week against Oklahoma, tied for the third-most in Oklahoma State history and the most ever for a Cowboy freshman. He was named Big 12 newcomer of the week.
Kansas: Hosts Texas on Saturday.
Oklahoma State: Plays at Kansas State on Saturday.