McMahon scored three times in a 10-minute span, including the go-ahead goal with 8:51 to play and the Cardinal held on during the frantic final seconds.

Stanford, which lost three times to the Trojans last year, defeated USC for the third time this season. The three victories were decided by a combined five goals and included a triple-overtime game. All three involved big-second half comebacks by the Cardinal.

The second-seeded Cardinal (14-4) advances to meet top-seeded Colorado (13-4) in the inaugural Pac-12 Tournament Championship game at 11 a.m. on Sunday. The Buffaloes won both regular-season meetings.

Sophomore Daniella McMahon recorded her first career hat trick, scoring three goals during a dramatic second-half comeback and leading 13th-ranked Stanford lacrosse to a scintillating 15-14 victory over USC in the semifinals of the Pac-12 tournament Friday in Boulder, Colo.

The Trojans responded by scoring five of the next six goals, including one from Menlo School grad Sophia Donovan, and led 11-9 with 19:33 to play. Donovan scored twice in the contest.

Buness scored the first goal of the second half, using 62 seconds to up the Cardinal's lead.

Senior Kelsey Murray scored twice after a goal from freshman Taylor Scornavacco and the Cardinal led at the break.

No. 3 seed USC (10-8) scored three in a row and led for the majority of the first half. But Stanford scored the last three before intermission, a portent of things to come.

Senior Allie DaCar made 10 saves, including seven in the second half. Junior Julia Massaro extended her school record with a team-high six draw controls and is up to 80 this season. Murray had two goals and two assists, while Kyra Pelton, Kelly Myers and Dillon Schoen each had three ground balls.

USC scored with 33 seconds left and then won the draw control but Stanford's defense did not allow a shot in the waning seconds.

Baiocco, Buness and senior Maggie Nick scored consecutive goals to knot the game at 13 with 11:37 left. McMahon followed by scoring twice to put the ball squarely in Stanford's court.

That's when McMahon and her Cardinal teammates went to work as Stanford scored the next five goals, including three in a 2:03 span to tie the game.

McMahon snapped the streak with a free position goal with 16:27 remaining, but USC responded to take its largest lead, 13-10, with 15:02 to go.

USC led 19-12 in draw controls and the Cardinal was out-shot, 32-26, but held the edge in ground balls 23-19.

Follow Palo Alto Online and the Palo Alto Weekly on Twitter @paloaltoweekly , Facebook and on Instagram @paloaltoonline for breaking news, local events, photos, videos and more.

Big-time rally gives Stanford shot at Pac-12 lacrosse title