This season, a typical University of Hawaii baseball game has few walks in the park.

The Rainbow Warrior pitchers are fourth nationally in fewest walks (2.21 per nine innings) entering tonight’s opener of a four-game series against Nevada at Les Murakami Stadium. The scarcity of walks and hits — their WHIP is 1.20, which is 23rd nationally — have helped boost the ’Bows to a 15-8 record.

“If we keep the walks-per-game average where it is, we’ll have the opportunity to stay in a lot of games because we’re not giving up freebies,” UH coach Mike Trapasso said. “That’s where it starts.”

And their pitching begins with their four starters, who have combined for a 2.55 earned-run average, 1.11 WHIP and 1.75 walks per nine innings. It also has created an enviable surplus problem. The past five weeks, the ’Bows have used a four-pitcher rotation of Brendan Hornung, Dominic DeMiero, Neil Uskali and Jackson Rees. But for Big West play, which begins next week, each series consists of three games.

Hornung, who has allowed three walks and struck out 51 in 46 2/3 innings, and DeMiero, who has a team-leading 1.91 ERA, are assured starting berths. Uskali and Rees will compete for the third spot. Against Nevada, Rees will pitch on Saturday and Uskali on Sunday.

Uskali’s ERA was 1.85 in his first four starts, but 9.00 in the past two. “Neil hasn’t pitched well at all in his last two outings,” Trapasso said. “Obviously, we’re looking at the whole body of work, and we know what he’s capable of doing. He’s already shown it. He needs to pitch better.”

The ’Bows have won all five games in which Rees has started, supporting him with an average of eight runs per game. “While Jackson had a good game and a quality start for us, he needs to pitch ahead in the count a little better than what he has his last couple times,” Trapasso said. Rees has issued a team-high 16 walks this season, including 13 as a starter.

“Both of them are more than capable of going out and being a weekend starter in the Big West, and that’s a good problem to have,” Trapasso said. “We’ve got a nice competition and we’ll see what happens. We’ll wait until after this weekend, and take a look where we are. Right now, it’s fun to have competition on your team.”

Trapasso had said the first 20 games would be used to cast roles. With 23 games in the books, Trapasso said, “I think the evaluation part has come and gone. We know what we have. It’s about trying to play well and clean some things up from last week. … The good thing about these kids is they’ve been able to stay on task. They’re very even-keeled in not getting too high when they win and not too low when they lose.”

The ’Bows lead Big West teams in drawing walks. They have struck out as many times — 124 — as they have reached on walks (99) and hit batsmen (25).

“For the first time in a long time, this late in the season, we’re actually at a 1:1 ratio,” Trapasso said. “If you can keep that at 1:1, you’re going to have a pretty good on-base percentage.”

The goal is for the on-base average to be 100 points higher than the batting average. UH is hitting .274, reaching base at .370. Trapasso said the improved hitting has “allowed us to win some games when we haven’t played brilliantly defensively and on the mound, which were games we may have lost the last couple years. When we weren’t scoring (in past years), we had to play a perfect game defensively and pitching-wise, and you just can’t do that in college baseball. It’s not realistic.”