OAKLAND, Calif. -- Houston Astros right fielder George Springer hit a career-high 29 home runs last year in 162 games.

Springer hit his 20th blast on Monday night in just his 65th game, a solo shot in the eighth inning of a 4-1 win over the Oakland Athletics at Oakland Coliseum.

Springer reached the 20-homer mark for the third time in his four major-league seasons, but this time he's on pace to shatter his home-run mark long before the season ends.

"I think just slowing everything down," Springer said of the key to increased power. "Just trying to get to first base for guys like (Carlos) Correa, (Jose) Altuve, (Carlos) Beltran. I know who's up behind me. It's been slowing me down a lot and I've been fortunate enough to hit some balls hard."

Jake Marisnick and Derek Fisher also homered for the Astros, and right-hander Brad Peacock pitched 5 2/3 strong innings. Marisnick gave Houston a 2-0 lead with a two-run blast in the fifth inning. Springer homered in the eighth, and Fisher added a solo homer in the ninth.

"I think it's a more controlled swing for him," Astros manager A.J. Hinch said of Springer. "He still has a tendency to swing hard and swing violently from time to time, but for the most part he's under control of his at-bats. He's a good guy getting a good pitch to hit, and he's not missing them.

"He can hit the ball out of the ballpark, from foul pole to foul pole, which will help him. You go opposite field here, that's a really, really tall task. It's a combination of a lot of things. He's a really good hitter and he knows his pitches he can drive."

Catcher Evan Gattis went 2-for-4 with two doubles and scored a run for Houston, which defeated the A's at the Coliseum for the seventh straight time and for the 12th time in their past 13 games overall.

Peacock (4-1), a former A's minor-leaguer, allowed one run and four hits. He walked two and struck out eight.

In six starts since moving from the bullpen to the rotation, Peacock struck out at least eight batters five times. He has 44 strikeouts in 28 1/3 innings.

"The slider's huge for me, working it off the two-seamer," Peacock said. "I think that's the key. I'm really not trying to strike anybody out. I'm just trying to make pitches and try to go deep in the game."

A's rookie right-hander Daniel Gossett (0-2) gave up two runs and six hits in 6 2/3 innings in his second career major-league start. He struck out six and walked none.

In his first start, Gossett allowed seven runs and six hits in 3 1/3 innings in an 11-6 loss at Miami on June 14.

"A lot more focus," Gossett said of his second start. "I realized that every pitch deserves every bit of focus I've got. I was able to stay focused throughout the game and on every pitch. That was a key learning point."

The last-place A's, coming off a four-game series sweep of the Yankees at home, fell 15 1/2 games behind the first-place Astros in the American League West. Houston opened a seven-game road trip after going 3-6 in a nine-game homestand.

The A's cut Houston's lead to 2-1 in the sixth inning. With one out, Matt Joyce lined a double to right off Peacock. After Chad Pinder walked, Jed Lowrie doubled to right center, scoring Joyce. Pinder tried to score, too, but he was thrown out at home after a relay from Springer in right to shortstop Carlos Correa to Gattis.

The speedy Springer cut the ball off on one hop in the alley, spun and quickly got the ball to Correa, who made a strong throw home.

"It starts with Springer, him cutting the ball off and having an acrobatic throw off his back leg to get the ball in so quickly," Hinch said. "And then Correa threw a strike. The three of them had to work together seamlessly. There wasn’t much room for error. When the ball was hit, I thought both guys were going to score ... but we fundamentally made the play."

Springer led off the eighth with a home run to right center against reliever John Axford. Fisher launched a home run into the right field seats off Josh Smith with one out in the ninth.

Astros relievers Will Harris, Chris Devenski and Ken Giles combined to blank the A's on no hits in the final 3 1/3 innings. Giles pitched a perfect ninth for his 17th save.

The Astros took a 2-0 lead in the fifth on Marisnick's two-run shot off Gossett. On a 2-2 count, Gossett threw a 94 mph fastball that tailed back over the middle of the plate, and Marisnick hit it 440 feet for his ninth home run of the season.

"Fastball out over (the plate), where Marisnick likes it," A's manager Bob Melvin said. "He had some pretty good swings. That's why I took (Gossett) out the third time when he came up. But it was down, at least it looked like it was down from my angle, but he squared him up pretty good. Other than that, just a few line-drive outs, but it was way better than what we saw the first time out."

NOTES: After the game, Houston optioned OF Derek Fisher to Triple-A Fresno, opening a roster spot for OF Josh Reddick, who will be activated from the seven-day concussion disabled list on Tuesday. ... A's rookie 3B Matt Chapman (left knee infection) missed Monday's game and is being treated with antibiotics. "We'll see how it does in the next 24 hours," said Nick Paparesta, Oakland's head athletic trainer. ... A's bench coach Mark Kotsay will take an indefinite leave of absence from the team to be with his daughter, Sienna, who was struck from close range with a tennis ball in her right eye last week and has experienced a partial loss of vision, general manager David Forst said. "Mark will stay with his family as they seek the opinions of specialists and he will remain as long as needed through recovery and the healing process," Forst said. "He's hopeful of returning at some point this season." Third base coach Chip Hale will serve as bench coach during Kotsay's absence, and Steve Scarsone, who had been a longtime minor-league manager for the A's until becoming a traveling instructor this year, will coach third base. Garvin Alston, a longtime pitching instructor in the organization, was hired as bullpen coach. ... Astros RHP Lance McCullers Jr. (lower back discomfort) threw a pain-free bullpen session and will likely come off the DL and return to the rotation at some point during the Astros' three-game series at Seattle, which begins Friday.