ST. LOUIS -- Kwamain Mitchell and Saint Louis found a way to pick apart the nation's top defensive team.
Mitchell scored 17 of his 21 points in the first half, leading Saint Louis to a 69-59 victory over Princeton on Wednesday night in the semifinals of the College Basketball Invitational.
The Billikens (23-11) will play Virginia Commonwealth (25-9) in the best-of-3 championship series beginning Monday.
"This was a nice win for us," Saint Louis coach Rick Majerus said. "These guys have won a lot of games."
Willie Reed added 20 points and 10 rebounds for the Billikens, who won for the 11th time in 14 games. It was his ninth double-double this season.
Mitchell triggered a 16-4 run over the final 7:25 of the first half to put Saint Louis ahead to stay, 38-29. The Billikens scored the last seven points of the half and the first eight of the second half against a usually aggressive defensive unit.
"We weren't as great defensively as we had been most of the season," Tigers guard Marcus Schroeder said.
The 69 points were the second-most given up this season by the Tigers, who lost 81-60 to California on Nov. 29. Princeton entered allowing an NCAA-low 52.8 points per game.
Saint Louis was 24 of 44 from the field (54.5 percent), becoming the third team to surpass 50 percent against Princeton this season.
Mitchell capped the 7-0 first-half run with a three-point play that gave the Billikens a 38-29 lead at the break. Reed began the second half with a short jumper before Cody Ellis and Kyle Cassity sank back-to-back 3-pointers to push the lead to 46-29.
Princeton missed its final nine shots in the first half and its first two in the second half.
The Tigers battled back to within 55-49 on a short jumper by Zach Finley with 4:36 left. But Reed answered with his fourth slam dunk of the night to halt the rally.
"I felt our defense played pretty well," Majerus said. "We were hard to score against."
Both teams reached the postseason for the first time since 2004.