KANSAS CITY, Mo. — Emanuel Sharp scored 19 points as No. 2 Houston defeated Colorado 77-68 in the Big 12 tournament quarterfinals on Thursday.The top-seeded Cougars struggled to secure a comfortable win against the Buffaloes, never stretching the lead to more than 14 points.The Cougars will face BYU in the first semifinal Friday night. BYU defeated Iowa State 96-92 in Thursday’s first game.Houston (28-4) had a balanced scoring attack. LJ Cryer and Milos Uzan each had 14 points, with Joseph Tugler adding 10.The 16th-seeded Buffaloes ended their season 14-20 after surprising ninth seed TCU in their first-round game and then knocking off No. 8 seed West Virginia in the second round. They were led by Andrej Jakimovski with 25 points and eight rebounds. Bangot Dak chipped in 10 points.The Cougars had trouble shaking the pesky Buffaloes. They didn’t match their largest first-half lead until Uzan’s layup with 11:36 left put Houston up 59-45.But even that was not enough to seal it, as Colorado scored six of the next seven points to get it back inside 10. Each time the Cougars extended it, the Buffaloes responded.