Syracuse would get out to as much as a 12-point advantage, but Marquette would fight back, getting as close as three, 21-18, off of a made jumper by junior forward Davante Gardner with 3:18 remaining in the first half.
Southerland's three with 1:07 to go in the opening half gave the Orange a two-possession edge on the Golden Eagles at the half, 24-18.
Coming out in the second half, Syracuse did not make a field goal until the 14:@4 mark, when Triche elevated for a layup.
But they made up for it as the clock ticked away, getting back out to a double-digit lead.
Back-to-back threes at the end sealed the win for the Orange, 55-39, as they head down to Georgia as East Regional Champions, still alive in the fight for the 2013 national championship.