It was a tight contest much of the way, but a 10-1 run over a 3:59 stretch midway through the second half put the Musketeers up by 10, 49-39. St. John's battled back to pull to within four, but could get no closer.
St. John's (18-11, 8-8), coming off a game Saturday against Villanova in which they shot just 32.2 percent, once again had trouble from the floor. They shot just 37.3 on the night, and have now dropped two straight, after winning nine of their previous 10.
JaKarr Sampson led the way for the Red Storm with 14. Orlando Sanchez had 11.
The teams battled through a low scoring first half in which neither led by more than five. Each side got a lift from their big men in the opening frame. Sanchez led the way for St. John's scoring all of his 11 points in the first, while Sampson added eight.
For Xavier, Stainbrook's 10 first half points came in only 10 minutes of action, as he picked up his second foul with 6:04 remaining and spent the rest of the half on the bench. But the Musketeers still managed to take a 31-30 lead to the locker room.
Stainbrook would go on to foul out of the contest with 3:00 to play, but the Musketeers still had plenty of firepower to prevail, thanks to the strong performance from Reynolds.
Rysheed Jordan did his best to keep the Red Storm in it, scoring nine of his team's first 15 points in the second half, on his way to 11 overall. The problem for the Red Storm was that it took 14:44 for them to score those 15 points.
St. John's was hurt by a subpar performance by junior guard D'Angelo Harrison. The team's leading scorer entering the night, Harrison was held to just four points on 1 of 11 shooting.
The Red Storm, who fell to .500 in the conference with the loss, will look to rebound on Sunday afternoon when they take on DePaul.