KINGSTON, R.I. - The overwhelming optimism about the potential for the University of Massachusetts men's basketball team after Saturday's win over Saint Louis took a sizable dent Wednesday night.

Last-place Rhode Island, which stunned Dayton Saturday, added the Minutemen to its victim list by delivering an 81-78 upset in overtime Wednesday at the Ryan Center.

UMass trailed for most of the extra session, but improbably had a late chance at a winning basket. After Chaz Williams made both free throws to bring UMass within 79-78 with 10.9 seconds left, Raphiael Putney intercepted Nikola Malesevic's errant inbounds pass for the Rams. Putney fed Williams, who drove into traffic.

Williams and UMass coach Derek Kellogg both thought the point guard had been fouled as the ball skipped out of his hands, but there was no call and Rhode Island snared the ball.

"I was looking for contact," Williams said. "I thought there would be a foul called but it didn't go that way."

The Minutemen were forced to foul and Malesevic (19 points) made both free throws. After Freddie Riley missed a long 3-pointer at the buzzer, the Ram fans rushed the court.

"The call wasn't made and that was pretty much the ball game," Kellogg said. "We got a nice steal and he drove it in the paint. On a certain day that might be a foul and on a certain day it's not. It's one of those things."

After his press conference, a TV in the media room was showing highlights of the game. Kellogg paused to watch the replay of Williams' drive to the basket to see if there was a foul. He didn't say a word, but shook his head in frustration as he walked out of the room.

"That was a huge loss," said Williams, who had 12 points, eight assists, five steals and nine turnovers. "We just came off a huge win. We didn't play UMass basketball."

The Minutemen (16-6, 5-3 Atlantic 10) had a chance to win at the end of regulation. Terrell Vinson made two free throws to tie the game at 67 with 1:09 left. Williams stole the ball from Orion Outerbridge and raced toward the other end. His layup was goaltended to put UMass ahead 69-67, but Outerbridge answered with 29.7 seconds left.

The Minutemen held for the last shot after a timeout with nine seconds left. Williams tried to drive but was cut off so he kicked the ball to Jesse Morgan in the corner. Morgan's 3-point attempt was off the mark, sending UMass to overtime for the first time this season.

Outerbridge led Rhode Island (5-18, 2-6 A-10) with 29 points and 11 rebounds.

Putney had 18 points, eight rebounds, six steals and three blocks for UMass, which plays at George Washington at 7 p.m. Saturday.

The Minutemen, who had shot free throws so effectively against Saint Louis, missed some big ones against the Rams and finished 15-for-25. Rhode Island outrebounded UMass 48 to 35 and turned 19 offensive rebounds into 18 second-chance points.

"We didn't make some plays today," Kellogg said. "We'd play good defense, but our second stab at the defense after their offensive rebounds wasn't quite so hot. Any time a team has 19 offensive rebounds, that's a hard game for you to win."

Outerbridge's 15 first-half points and a huge rebounding edge kept the Rams in the game early as the Minutemen looked poised to pull away. But after a Riley 3-pointer stretched the UMass lead to 28-22 with 5:36 left, Rhode Island went on a 14-4 run that included the last five points of the half, to take a 36-32 lead at intermission.

The Minutemen used a 14-2 run early in the second half to take a lead they held for most of the rest of regulation, but the Rams chipped away to set up the final sequence.

Matt Vautour can be reached at mvautour@gazettenet.com. Follow UMass coverage on Twitter at twitter.com/GazetteUMass. Get UMass coverage delivered in your Facebook news feed at http://www.facebook.com/GazetteUMassCoverage.