On Sunday afternoon, the Hawaii baseball team’s offense was matinee idle.

Cal State Northridge’s Matt Acosta pitched a five-hitter and issued no walks in a 2-0 victory at Les Murakami Stadium.

The Matadors won twice in this three-game series to improve to 19-24 overall and 7-8 in the Big West. In absorbing a shutout for the second Sunday in a row, the Rainbow Warriors lost their second consecutive series and dropped to 22-17 and 8-7.

“We didn’t hit,” UH coach Mike Trapasso said. “We didn’t play well all series outside of the first game. We hit (on Saturday) and pitched terribly. We pitched good (Sunday) but didn’t hit. That’s baseball. … It was a bad series. We have to regroup, and hit and pitch well on the same day.”

Acosta, a right-handed junior, had not pitched more than seven innings in his previous nine starts. But on Sunday, he relied on a sinker that was breaking low and inside against right-swinging hitters.

“We couldn’t lay off it because it was so good, so late,” Trapasso said. “It was outstanding. I could see why he’s tough on right-handers because the ball is running down and in on our righties.”

UH’s right-hitting batters were 3-for-20 against Acosta.

Asked about his best pitch, Acosta said, “just strike one. You throw strike one, you’re helping yourself out already.”

Acosta threw first-pitch strikes to 20 of 31 hitters.

“Really, I was just pounding strikes and letting my defense get the job done,” Acosta said. “When you’ve got guys like that playing behind you, it makes the game that much easier.”

The ’Bows threatened in the fifth and eighth innings when they trailed 1-0. With Ethan Lopez on third, Acosta induced a groundout to end the fifth. In the eighth, the ’Bows had runners at the corners with one out. Maaki Yamazaki hit a bouncer up the middle. For the ’Bows, it proved to be a little chop of horrors, with shortstop Alvaro Rubalcaba fielding the ball, stepping on second and then firing to first for the inning-ending double play.

“We had opportunities,” Trapasso said. “We just didn’t do anything with them. The opportunities were few and far between.”

The ’Bows also were understaffed for the series. Logan Pouelsen, a swing pitcher, was not available to pitch this series because of tenderness in his right (throwing) arm. Then on Saturday and Sunday, the projected starting pitchers — Neil Uskali and Dominic DeMiero, respectively — were scratched after experiencing arm tenderness during pregame warm-ups in the bullpen.

“That’s something I’ve never seen in 30 years of coaching at the Division I level,” Trapasso said. “I’ve never seen it in pro ball. I’ve never seen it when I was in college, where you had two days in a row when guys went down while throwing in the ’pen because they were sore. I’ve never seen it before, and probably will never see it again.”

Cade Smith started on Saturday and Jeremy Yelland on Sunday, depleting the ’Bows bullpen. Yelland lasted 22⁄3 innings, allowing one hit but walking two and hitting four Matadors. Before exiting, Yelland relinquished a run on an RBI groundout.

“Jeremy is not going to get hit,” Trapasso said. “He just has to throw strikes. He was his own worst enemy.”

Kyle Hatton replaced Yelland, and did not allow a run in 31⁄3 innings. But with the lightened bullpen, closer Dylan Thomas was summoned with one on and no outs in the seventh inning. Thomas gave up a sacrifice fly and his first walk of the season while throwing a season-high 54 pitches. “You can see in that ninth inning, he was fatiguing,” Trapasso said.

Now the ’Bows will wait on whether Pouelsen, Uskali and DeMiero will be available to pitch in this week’s series against Cal Poly.

“It’s going to be an anxious week waiting to see what’s up with Neil and Dom and Logan,” Trapasso said.