OLEAN, N.Y. (AP) - In a matter of a moment, Massachusetts guard Chaz Williams lost the ball, his headband and then his focus.
By the end, Williams and the 21st-ranked Minutemen lost their second of three games in a 78-65 defeat at St. Bonaventure on Wednesday night.
Williams, who entered the game averaging 15.9 points and 7.4 assists, was rendered a non-factor in the face of a stifling defense. He finished with 11 points, six assists and turned over the ball four times before fouling out with 1:39 remaining.
"They did a good job on him," UMass coach Derek Kellogg said. "He did get a little frustrated. We just kind of have to play through those bumps and grinds when we get in there."
The Minutemen (17-3, 4-2 Atlantic 10) had little in response. Trey Davis led them with a career-best 18 points in a game the Minutemen hit 25 of 59 attempts, committed 17 turnovers and were unable to establish their fast-paced tempo attack.
The Bonnies (13-8, 3-4) snapped a 24-game skid against ranked teams dating to a 57-56 win over No. 20 Temple on Jan. 15, 2000.
Williams' struggles highlighted how much the Minutemen rely on him on offense.
"Trey stepped up and did what he was supposed to do," center Cady Lalanne said. "But not having Chaz out there kind of affected us a little bit."
Williams lost his focus on consecutive positions 8 minutes into the second half. Both times he lost the ball while attempting to drive the lane. The second time, Williams not only lost the ball, but also had the purple headband stripped off his head.
While Williams was busy complaining with the officials, Denzel Gregg was capping a fast break with a dunk at the other end to put St. Bonaventure up 45-38 with 12:35 remaining.
After a UMass turnover, Williams grew upset and was issued his fourth foul for hacking Youssou Ndoye, who hit both free throws.
Williams spent the next 6 minutes on the bench with a towel over his head.
"He did get a little frustrated," Kellogg said. "When you knock his headband off, I think he gets a little frazzled."
St. Bonaventure finally proved it could hold on to a lead in the second half.
They were still stung by the memory of blowing a 13-point, second-half lead in a 73-68 loss at UMass on Jan. 11. And then there was their last outing, an 83-81 loss at Duquesne on Saturday that was decided on Derrick Colter's desperation 3-pointer at the buzzer.
"It was a great victory," Bonnies coach Mark Schmidt said. "Being able to beat that team by 13 points coming off a tough game at Duquesne speaks volumes about the character of our players."
The win was keyed by a workmanlike effort in which Charlon Kloof scored 14 points to lead a group of five players who scored in double digits. Marquise Simmons had nine rebounds. Youssou Ndoye scored 11 of his 12 points in the second half.
The crowd of 3,881 began yelling "Yes! Yes! Yes!" with 30 seconds left, and then stormed the court with 2 seconds remaining. The court had to be cleared for a moment before play resumed, and the fans charged back out once the final buzzer sounded.
After trading leads six times through the first half, and again in the opening minute of the second, the Bonnies, who are 9-1 at home, went ahead for good with 18:47 left.
That's when Matt Wright hit a jumper from the top of the key to give St. Bonaventure a 28-27 lead.
The crowd began sensing the upset with 5:26 remaining when Dion Wright capped consecutive drives with baskets to cap an 11-3 run. The Minutemen seemed to have gained momentum on Raphiael Putney's dunk that closed the gap to 53-51 with 8:46 left.
With St. Bonaventure up 55-54, Andell Cumberbatch helped turn the tide by banking in a 3-pointer with 1 second left on the shot clock with 7:20 remaining.
"We've got to just saddle up and play a little better," Kellogg said. "I think everybody can see we're not playing as well as we could be. But we're going to right the ship."