OAKLAND -- About three hours before Shohei Ohtani took the mound for his first start in the Majors, Michael Trout turned to his Japanese teammate in the Angels' clubhouse and expressed his excitement about the top prospect's impending pitching debut.

"Sho time!" Trout said.

Trout wasn't the only one eagerly anticipating Ohtani's outing. Two hundred and forty members of the Japanese media packed into the Coliseum on Sunday afternoon for the occasion, while many more tuned in at 5:05 a.m. on Monday to watch the live broadcast back in Japan.

They were treated to a performance that was largely dominant but also imperfect, a fitting outcome for a 23-year-old rookie who is undertaking a groundbreaking endeavor in front of an international audience.

Three days after making his MLB debut as the Angels' designated hitter on Opening Day, Ohtani picked up his first win as a pitcher by allowing three runs over six innings in the Halos' 7-4 victory over the A's.

With his outing, Ohtani became the first Major League player to start as a non-pitcher on Opening Day and then start as a pitcher within his team's first 10 games since Babe Ruth with the Red Sox in 1919.

"Personally, I feel like I've gotten off to a good start," said Ohtani, who went 1-for-5 as a left-handed hitter on Thursday. "Obviously, the team went 3-1 on their first road trip, so very happy with the results."

The right-hander gave up just three hits -- all in the second inning -- including a three-run homer to Matt Chapman . Ohtani induced 18 swings and misses, a total surpassed by Angels starters only three times last season. Over the past 10 seasons, only Alex Colome of the Rays induced more swings and misses in an MLB debut when he did it 20 times in 2013.

Ohtani retired 14 of the next 15 batters he faced, helping the Halos secure a series victory in the opening weekend of their 2018 campaign. Ohtani, whose fastball averaged 97.8 mph and topped out at 99.6 mph, struck out six, walked one and threw 92 pitches (63 strikes).

"I think you saw the talent and you saw him being able to put pitches together," manager Mike Scioscia said. "You can see how he can get hitters out, not just the velocity but all his pitches. He used everything. Outside of one stretch of three hitters in the second inning, that's about as well as you can pitch."

Ohtani underwhelmed in his five starts as a pitcher during Spring Training, but he shone on Sunday, unleashing a blazing fastball and showcasing vicious splitters and sliders. He had trouble throwing his splitter during his spring outings, but catcher Martin Maldonado said his pitches behaved differently away from the dry conditions of Arizona.

"I've been in Arizona for 14 Spring Trainings," Maldonado said. "I know a lot of people who have trouble with split fingers and curveballs. I knew he had a good splitter. I knew coming in, the air is different, so I think his pitches are going to be different here than in Arizona."

Ohtani recorded three of his first four outs via strikeout and fanned the first Major League batter he faced, Marcus Semien , on a splitter. But he was tested in the second after allowing back-to-back singles to Matt Joyce and Stephen Piscotty and a three-run homer to Chapman on a hanging slider, which gave the A's a 3-2 lead.

"Obviously, nobody had really faced him before," Chapman said. "The first time you face a guy, you've kind of got to feel it out. But my plan was to kind of attack strikes. He looked like he was throwing strikes right away. We were trying to jump on the first good pitch we saw because we know he has a lot of good stuff to put guys away, so wanted to get a good pitch and try and jump on him early.

"Unfortunately, we weren't able to do that too much today. He had some good stuff."

Still, the mistake didn't faze Ohtani. He rebounded by cruising through the next four innings, yielding only a one-out walk to Joyce in the fourth.

"After that three-run shot, Scioscia came up to me and said I'm doing fine," Ohtani said. "Just a little bump from here on out. I was able to talk to Maldonado between each inning and try to communicate as much as we can. Obviously, the hitters got me the lead, so I was able to get through it."

Ohtani received plenty of support from his offense, which generated seven runs on 13 hits to give him his first win.

"I'm really happy for him," shortstop Andrelton Simmons said. "It's a good way to start. He still has a long ways to go, so I hope he doesn't ease up and stays hungry."