ANAHEIM -- After throwing complete games in two out of his last three starts with Double-A Rocket City, right-hander Jack Kochanowicz had some momentum coming into his Major League debut against the Mariners.

But Kochanowicz found out that big leaguers are tougher to put away, as he struggled in his first career start, an 11-0 loss on Thursday at Angel Stadium. Kochanowicz, ranked by MLB Pipeline as the club’s No. 7 prospect, went three innings, allowing five runs on seven hits and two hit batters. Kochanowicz, though, believes he can learn from the outing. He was still excited to achieve his goal of reaching the Majors and being able to pitch in front of his family and friends.

“Definitely a dream come true but not exactly what I wanted,” Kochanowicz said. “But I feel like it’s a good outing to build off of and keep going.”

The 23-year-old had trouble in the opening frame, allowing four straight hits to start the game. But Kochanowicz was helped by the Mariners running into an out at third base. He loaded the bases after hitting Luke Raley on the foot with an 0-2 curveball and had a real chance to get out of the inning with minimal damage after inducing a potential double-play grounder to third. But Luis Guillorme tagged third and made an errant throw to first to allow a run to score and keep the inning alive.

The Mariners took advantage, as Jorge Polanco ripped a two-run single to left-center with two outs. Polanco’s hit came on an 0-2 changeup. Three of Seattle’s five hits that inning came with two strikes. Kochanowicz, however, recovered to strike out Mitch Haniger to end the inning and record his first big league punchout.

He looked much better with a 1-2-3 second inning but was greeted by a solo homer from Cal Raleigh to open the third. He gave up a double to Julio Rodríguez and again hit Raley on the foot with an 0-2 curveball. But he got France to fly out to right before getting Polanco to ground into a double play.

“It's just about continuing to trust myself,” Kochanowicz said. “It's the main thing and not letting it do too much in my head, but just trusting myself. It’s the same game, but I have to just trust myself.”

It was the final inning for Kochanowicz, who threw 60 pitches, with 41 going for strikes. Being around the zone wasn’t his issue. It was more about putting away hitters. The 6-foot-7, 228-pounder’s fastball clocked as high as 97.2 mph, as he has plenty of velocity, but he’ll have to work on his location and secondary stuff to succeed in the Majors.

“He has a lot of sink on his ball, but in that first inning, he left it too high,” said manager Ron Washington. “He came out in the second inning and sort of cleaned up a little bit. But they just started working him pretty good. I didn't think it was going to get any better. I thought he went far enough. It’s an experience for him.”

Kochanowicz, a third-round pick out of Harriton High School near Philadelphia, has a career 5.54 ERA in 326 innings in the Minors. But he had been pitching much better recently, throwing complete games on June 26 and again on Saturday to earn the promotion.

It was the fourth straight short start for the Angels, as Davis Daniel went 3 2/3 innings on Monday, Roansy Contreras lasted two frames on Tuesday and Griffin Canning tallied 4 1/3 innings on Wednesday. It forced them to use long reliever Kenny Rosenberg, who was recalled from Triple-A Salt Lake on Wednesday to provide some depth. He allowed six runs over six innings in his season debut.

It could have a domino effect of the Angels bringing up 2021 first-round Draft pick Sam Bachman from Double-A to start on Sunday. Bachman has been pitching well, posting a 4.05 ERA over his last three outings. He was scratched from his start on Friday to give the Angels an option for the series finale. Contreras could also be an option, but he has struggled during his brief taste in the rotation, with an 8.22 ERA in 7 2/3 innings over three starts.

“We haven’t decided yet,” Washington said. “We’ll just wait and see.”