The Big West Tournament next week is now a must-win situation for the Hawaii men’s volleyball team to continue its season.

The fifth-ranked Rainbow Warriors finished 5-5 in Big West play after UC San Diego swept Hawaii 27-25, 25-21, 25-20 on Saturday in the regular-season finale for both teams at LionTree Arena in La Jolla, Calif.

Junior Keoni Thiim had a team-high 12 kills for the Rainbow Warriors, who will be the No. 3 seed in the BWC tournament and host No. 6 UC Santa Barbara in the second first-round match on Thursday at SimpliFi Arena at Stan Sheriff Center.

UC San Diego (12-14, 4-6) earned its third win over Hawaii in four seasons to claim the No. 4 seed in the tournament and will play No. 5 Cal State Northridge in the opener on Thursday.

Long Beach State swept UC Irvine on Saturday to earn the No. 1 seed over the Anteaters, who will play the winner between Hawaii and UCSB on Friday.

UH, which is 22-6 overall, dropped to 5-5 since losing Spyros Chakas to a season-ending injury. It will need to claim the Big West’s automatic berth into the NCAA Tournament to have the chance to reach the national championship match for a fifth straight season.

Chaz Galloway added seven kills in 14 swings against UCSD after replacing Louis Sakanoko at outside hitter in the second set.

Alaka’i Todd had six kills and middle Guilherme Voss also had six kills in just eight swings.

Voss and fellow middle Kurt Nusterer combined for 10 kills in 13 swings.

Sebastian Lara had a match-high 14 kills and Anthony Cherfan had 13 for the Tritons, who hit .352 for the match. Hawaii hit .337.

Hawaii held the advantage in digs, 31-22, but the Tritons had nine aces to Hawaii’s four.

Thiim started the match behind the service line and had an ace during an opening 4-0 run.

The first set was tied eight times, with the last at 25-25 before the Tritons took the set on a service error by Sakanoko and a kill from Lara.

UH led 10-7 in the second set before the Tritons went on an 8-2 run to take a 15-12 lead at the media timeout.

Jim Garrison followed with back-to-back aces and the Tritons never led by fewer than three points the rest of the set as Josh Schellinger ended it with a kill to go up two sets to none.

Hawaii hit .478 in the third set and scored 14 points on kills, but the Tritons hit .611 and took advantage of six service errors by UH.

The final four points of the match all came on service errors.

Hawaii dropped to 12-5 overall against the Tritons in La Jolla, Calif., after winning the first 18 matches.

The five losses in conference play are the most for the Rainbow Warriors since joining the Big West in 2018.