Chaz Williams scored 20 of his 22 points in the second half as Massachusetts rallied to defeat Siena 82-78 Friday night.
After Williams made his first basket with 5 seconds left in the first half, the Saints (3-6) took a 41-35 lead into the break in the Hall of Fame Holiday Showcase.
Siena still led 49-38 with 16:45 to play when the Minutemen (8-3) used a 19-5 run, capped by a Raphiael Putney dunk, to gain a 57-54 advantage with 11:25 left.
Freddie Riley hit three 3-pointers during the spurt, and tied his career high of six en route to 20 points.
The Saints regained a four-point lead, but UMass pushed ahead for good on Williams' three-point play with 3:06 remaining.
Siena's Kyle Downey scored 23 points and OD Anosike had his fifth straight double-double with 22 points and 14 rebounds, including six offensive.
The Minutemen lead the series 6-1.
