Xavier (17-12, 9-6 A-10) ended a long winning streak for the second time in eight days. The Musketeers snapped Memphis' 18-game streak at the Cintas Center last week.
This one kept the A-10 race open heading into the final weekend.
The Billikens (23-6, 12-3) wasted a chance to win a share of a conference title for the first time since 1970-71 in the Missouri Valley. Their last outright title came in 1956-57. They could have clinched the No. 1 seed in the conference tournament with a win on Wednesday.
Instead, they fell into a first-place tie with No. 21 VCU, which beat Richmond on Wednesday. Saint Louis beat VCU during its 11-game winning streak for the head-to-head advantage. Saint Louis finishes the season at home against third-place La Salle on Saturday. VCU is at Temple on Sunday.
The Billikens tied it on Jordair Jett's tip-in with 11 seconds left in regulation, but they managed only one field goal in overtime. Taylor had a dunk and four free throws as the Musketeers pulled ahead 74-62.
Kwamain Mitchell led Saint Louis with 17 points. Cody Ellis, the Billikens' top 3-point shooter, missed all of his 15 shots -- 11 behind the arc -- and finished with four free throws.
Saint Louis beat the Musketeers twice last season, including a 73-68 win at the Cintas Center that snapped Xavier's A-10-record streak of 43 straight conference wins at home. The Musketeers pulled this one out on a night honoring their three seniors, including Taylor.
The rematch featured the conference's two stingiest defenses. Saint Louis leads the league and is ranked 19th nationally, allowing only 57.9 points per game. Xavier is second in the A-10, allowing 62.3 points. Those stingy defenses were locked in during the first half, which ended with the Billikens leading 24-20 -- the seventh time that Saint Louis has held an opponent to 20 or fewer in the opening half.
Junior forward Dwayne Evans has led the Billikens' offense during the winning streak, averaging 16.5 points. He picked up his third foul and went to the bench with 18:52 left, having scored five points.
Xavier never trailed after putting together the game's first significant run, scoring 10 straight points for a 37-29 lead with 11:47 left. Brad Redford hit a 3 to finish the spurt as Saint Louis went more than 6 minutes without a point.
Evans scored nine consecutive points, keeping the Billikens close. Xavier point guard Dee Davis missed two of his four free throws in the final minute, and Jett's tip-in with 11 seconds left tied it at 59.