The first Friday of May was a day of dismay for the Hawaii baseball team.

“I’m embarrassed by the way we played today,” UH coach Mike Trapasso said of the Rainbow Warriors’ 12-4 road loss to Cal Poly at Baggett Stadium in San Luis Obispo, Calif. “I’m embarrassed by the way I coached today. I am beyond words for the poor job I did in preparing our guys.”

The Mustangs exploited every UH mistake to win the opener of the three-game series and maintain their footing atop the Big West standings. The Mustangs are 21-21 overall and 11-2 in the Big West. The ’Bows fell to 18-23 and 7-9.

The Mustangs have been hazers since the ’Bows’ initial Big West season in 2013. The Mustangs have won all six series between the teams, with the edge now at 15-4, including 8-2 at Baggett Stadium. But for a half inning — the top of the fifth — the ’Bows appeared to stand up to their tormentors. The ’Bows scored all of their runs that inning. Third-string shortstop Jack Kennelly tied it a 3 with a two-run single, then scored from second on a wild pitch.

But the Mustangs tied it at 4 when Jack Kuzma was struck by a Cade Smith pitch to open the fifth, went to second when Connor Gurnik beat out what was supposed to be a sacrifice, and scored when a relay throw ended up in the UH dugout.

The Mustangs scored three in the sixth to take a 7-4 lead, and moved out of reach with two runs in the seventh and three in the eighth.

“The last three innings were a complete circus and, I guess, I’m the ringmaster,” Trapasso said.

In those three innings, the Mustangs drew seven walks. They scored runs on a balk, an error, a wild pitch and Tate Samuelson’s two-run homer.

There also was a flyball that was misplayed into a three-base error, a bunt that became a single when first base was left uncovered, and a pitch that was not blocked.

“You get a check list of everything you can do poorly, and then make some stuff up and put it in the end, and you can check that box, too,” Trapasso said.

Both starting pitchers managed to keep it close despite not having their best ammunition. Trapasso said Smith struggled with his arm slot, which led to inconsistency with secondary pitches. Smith pitched five innings, relinquishing four runs, three of them earned. Cal Poly freshman Chase Watkins did not allow a run in the first four innings, relying on a 12-6 o’clock change-up in which the directional movement averaged 16 inches. But Watkins was charged with all four UH runs in the fifth.

“Being in the middle of a dogfight for five innings, and then going to the bullpen and just watching us give the game away with seven walks in three innings is beyond painful, beyond disappointing. It starts with me and the poor job I did getting our guys ready tonight.”

UH’s four relievers combined to throw strikes on 47 of 100 pitches while allowing eight runs in three innings.

“It’s a whole litany of things we did wrong today,” Trapasso said, “and it starts with me.”

Today’s middle game of the series starts at 1 p.m. Aaron Davenport will be UH’s starting pitcher.