Jesse Morgan had 12 and Williams finished with 10 for UMass (9-3), which has won six straight games. The Minutemen also secured their seventh straight road victory, the program’s longest road streak since the 1997-98 season.
UMass led 37-29 at intermission but watched Miami (5-7) open the second half on a 9-2 run, cutting the deficit to 39-38. From there, the teams battled through eight lead changes and five ties until Williams’ jumper gave UMass the lead for good, 70-69, with 1:12 left.
Miami had a chance to tie but Quinten Rollins missed a free throw and Will Sullivan could not convert a layup as time expired. The Redhawks shot 2 for 9 over the final 6 minutes.
Allen Roberts led Miami with 21 points.