KANSAS CITY, Mo. — As they did in their first two meetings against Oklahoma State, the Kansas Jayhawks built a double-digit lead. And, as they did in their first two meetings with Oklahoma State, they blew the lead.But Kansas held on to beat the Cowboys 77-70 in overtime of the teams’ rubber match in the Big 12 quarterfinals Thursday afternoon at the Sprint Center. The Jayhawks (24-8, 14-4) held Oklahoma State (21-12, 8-10) to 31 percent shooting in the first half before they saw what was once an 11-point advantage slip through their fingers. “We haven’t defended them very well in the second half all three games,” Kansas coach Bill Self said. “They came out and shot 52 percent in the second half. We didn’t guard them as well, but the law of averages should prevail.”Prevail it did after Andrew Wiggins scored the last of his 30 points on a step-back turnaround jumper with 1:04 to play in regulation, tying the game at 67. The Big 12 freshman of the year scored 30 for the second consecutive game after not reaching the 30-point mark in any of Kansas’ first 30 games. “My shot was falling the whole game,” Wiggins said. “They cut off the baseline. My step-back is one of my main moves I like to do. It just fell through.”The score remained tied into overtime, when the Jayhawks clamped down on defense once again. The Jayhawks are without Joel Embiid, their leading rebounder and shot-blocker who is expected to miss the first week of the NCAA Tournament with a back injury. But they held the Cowboys to 1 of 8 shooting and forced two turnovers while committing none in the extra period. “They were giving me open shots, but the shots just weren’t falling tonight,” said Oklahoma State’s Marcus Smart, who scored 14 points on 4 of 14 shooting in the loss. “I took some good shots, took some bad shots. But the shots I took that were good just weren’t falling for me.”Wiggins didn’t score in overtime but has averaged 24.3 points on 54 percent shooting in the four games Embiid has missed this season, while shooting 43 percent in all other games.Kansas, which is trying to win its 10th Big 12 tournament title, improved to 17-1 in conference tournament openers. Oklahoma State, which didn’t score in the final 4:08 of overtime, fell to 0-4 in overtime games this season, all against Big 12 opponents.The Jayhawks will play fourth-seeded Iowa State at 6 p.m. Friday.