Seventh-seeded Saint Mary’s rallied from a sluggish offensive start and a second-half deficit of 12 points to upend No. 10 seed Vanderbilt 59-56 in the first round of NCAA Tournament East Region play on Friday in Cleveland.The Gaels (29-5) fell behind 39-27 just before the first media timeout of the second half when Vanderbilt’s Tyler Tanner connected on a 3-pointer. Saint Mary’s chipped away at the deficit over the ensuing eight minutes, however, embarking on a 16-4 run.That set up a tightly contested final eight minutes, during which Saint Mary’s led most of the way but never by more than six points.The Commodores (20-13) got 3-pointers from Devin McGlockton and Tyler Nickel in the final two minutes, bringing Vanderbilt to within a basket. Saint Mary’s Luke Barrett missed a jumper with 30 seconds remaining, but teammate Mitchell Saxen came up with the offensive rebound in traffic — one of his 11 boards on the day — and drew a foul.Saxen made 1 of 2 free throws, giving Vanderbilt a final possession to force overtime. Jason Edwards missed a contested step-back 3-point attempt, and McGlockton’s clean look off the offensive rebound was no good.Jordan Ross skyed for the rebound to seal Saint Mary’s third first-round win in the last four years.