Monday, the Waves (18-12) play No. 7 Gonzaga, which defeated San Francisco, 81-72. It will be Pepperdine's first semifinal appearance since 2004.
Davis' layup with 2:05 left gave the Waves a 48-45 lead. Brandon Perry's dunk cut the margin to one with 45 seconds remaining. After Davis was thwarted on a drive, San Diego's Johnny Dee put up a floater that missed as did a putback by Vasa Pusica with two seconds left. Shawn Olden sank two free throws for the final score.
The Toreros (15-16) had a 24-18 lead at halftime with both teams shooting in the low-30% range. Pepperdine warmed up to 48% in the second half but not San Diego, which hung in with 19 offensive rebounds for the game.
Gonzaga 81, San Francisco 72: Przemek Karnowski scored a season-high 24 points and Kyle Wiltjer added 19 to lead the Bulldogs (30-2).
Gonzaga next faces Pepperdine, which it swept during the regular season, winning 78-76 and 56-48.
Gonzaga struggled offensively in the first half and trailed 41-39 six minutes into the second half before going on a 16-0 run. At that point, the Bulldogs had a 58-42 lead and were never threatened.
Tim Derksen and Mark Tollefsen led San Francisco (14-18), the tournament's eighth seed, with 21 points each. Devin Watson scored 17.
Gonzaga point guard Kevin Pangos, the WCC player of the year, scored 10 points and added five assists before fouling out.
Portland 69, St. Mary's 52: Kevin Bailey scored 16 points, Jason Todd added 14 and the sixth-seeded Pilots surprised the Gaels. Portland (17-14) came into the tournament on a four-game losing streak. The Gaels (21-9) had beaten Portland nine consecutive times and had won all four meetings in previous WCC tournament games.
BYU 78, Santa Clara 76: Tyler Haws made a jumpshot with six seconds remaining to break a 76-76 tie. He led all scorers with 30 points.