OAKLAND, Calif. -- After giving up eight runs and lasting only 2 2/3 innings in a blowout loss at Boston on May 10, Oakland A's rookie left-hander Sean Manaea decided it was time for a new look and a fresh start.

Manaea got his first hair cut in a year, going from wild man to clean-cut, thanks to a stylist in Tampa, Fla.

Then he took the mound Monday night when the A's opened a seven-game homestand against the Texas Rangers and pitched a gem, earning his first major league victory.

Manaea gave up one run over 6 2/3 innings, Marcus Semien hit his 10th home run of the season, and the A's defeated the Rangers 3-1 at the Oakland Coliseum.

"It's a dream come true, you know?" Manaea said. "Getting that first one, it's huge. I'm really glad I got to do it at home."

Manaea (1-1) came into the game with an 11.37 ERA after giving up 16 earned runs in his first three major league starts. On Monday, he allowed four hits, struck out three and walked one while sporting his new hairdo.

"First three starts didn't go as well as I wanted them to, and as a team, we were kind of struggling. I just felt like it was time for a change," said Manaea, who came to the A's from the Kansas City Royals in the Ben Zobrist deal on July 28.

This was the type of performance that the A's hoped to get from Manaea this season.

"We thought at some point in time this year we'd see him," A's manager Bob Melvin said. "We weren't sure how quickly, but he got here in a hurry. I think as far as his stuff went and command, where he was throwing the ball, this was by far his best."

Rangers left-hander Derek Holland (3-3) bounced back with a strong outing after back-to-back poor performances. He gave up two runs on three hits over six innings, striking out one and walking one. Holland didn't make it out of the third inning in either of his previous two starts.

"I kept plugging away," Holland said. "A lot of positives in this start. I'm encouraged."

The A's took a 2-0 lead in the fourth, but Texas scored a run in the seventh. Adrian Beltre and Ian Desmond hit back-to-back singles, then advanced on a groundout. Drew Stubbs brought Beltre home with a sacrifice fly.

Semien answered with a solo shot with two outs in the bottom of the inning off right-hander Luke Jackson, who was called up Monday from Triple-A Round Rock. Semien drilled Jackson's 95 mph fastball over the 400-foot sign in center.

"I faced him in the past, in the minor leagues," Semien said. "He's added a little cutter. Try to see it up. He's got a good downer breaking ball, so I was trying to see the ball up, and I got one that was a fastball, four-seamer. He supplies the power because he throws pretty hard."

A's left-hander Sean Doolittle struck out the only batter he faced to end the seventh. John Axford pitched a scoreless eighth, and Ryan Madson a perfect ninth for his 11th save in 11 chances.

The A's struck for two runs in the fourth to open the scoring.

With one out, Holland hit Billy Burns with a pitch after getting ahead 1-2 in the count. Josh Reddick blooped a single to center for Oakland's first hit of the game, moving Burns to second, and Danny Valencia walked to load the bases.

Khris Davis hit a sacrifice fly to right in a nine-pitch plate appearance, bringing Burns home. Billy Butler then lined a single to center, driving in Reddick.

"His struggle was finding the one out pitch in that inning," Rangers manager Jeff Banister said of Holland. "It was a long inning, and that presented a challenge. He left the one pitch up over the zone for Butler. But he was much better tonight."

So was Manaea, in large part because he commanded his fastball and his changeup after going back to a grip he used in college.

"It feels a lot better in my hand, and it just feels like it's coming out like a fastball," Manaea said. "I feel like I'm able to control it and throw it for strikes. It all came together today."

NOTES: Rangers 2B Rougned Odor said he expects to be suspended "a couple games" but has no regrets for punching Toronto's Jose Bautista on Sunday during an eighth-inning brawl. ... Rangers RHP Tom Wilhelmsen was demoted to Triple-A Round Rock. RHP Luke Jackson was called up to replace him and gave up one run on one hit over two innings. Wilhelmsen went 2-2 with a 9.98 ERA in 17 relief appearances and allowed six home runs and 17 runs. ... A's RHP Jesse Hahn will be called up from Triple-A Nashville to start against the Rangers on Tuesday, manager Bob Melvin said. C Josh Phegley (sore right knee) will go on the disabled list, and LHP Eric Surkamp, who was scheduled to start Tuesday's game, will go to Nashville and rejoin that rotation. ... A's RHP Henderson Alvarez had "his first little setback" in his recovery from July 28 shoulder surgery, Melvin said. Alvarez experienced some soreness in his shoulder during his latest rehab start for Nashville, and he might undergo an MRI exam.