David Fletcher homered and drove in three runs for the Angels, who dropped the opener 2-1 as Ty France hit a two-run homer and George Kirby struck out eight over six innings for Seattle.
In the nightcap, Taylor Ward got the scoring started in the third with an RBI double that drove in speedy Magneuris Sierra from first base. Ward came home later in the inning on Max Stassi’s single.
Moniak launched a solo shot in the fourth, making it 3-0 with his third major league homer.
The top pick in the 2016 amateur draft, Moniak was acquired from Philadelphia at Tuesday’s trade deadline in a deal for pitcher Noah Syndergaard. The 24-year-old outfielder also went deep Thursday against Oakland but began the day a .131 career hitter in 99 at-bats over 50 big league games.
Luis Torrens put the Mariners on the board in the fifth with a home run to right-center against Detmers, his first of the season.
Detmers (4-3) was dominant early, allowing just one hit through four innings. After the hiccup in the fifth, Detmers settled back in. He gave up six hits overall and struck out seven.
Fletcher extended the Angels’ lead to 5-1 with a two-run homer off starter Chris Flexen in the sixth.
Flexen (7-9) pitched six innings, allowing five earned runs on six hits and two walks with five strikeouts.
Mariners reliever Matt Brash tossed a scoreless seventh, but left-hander Brennan Bernardino allowed two runs in the ninth — one on an RBI single from Fletcher, the other on a bases-loaded sacrifice fly by Shohei Ohtani.
In the first game, Moniak gave the Angels a one-run lead with an RBI single in the second, but France’s third-inning homer into the left-field bullpen put the Mariners ahead for good. The go-ahead drive was France’s 14th homer of the season and his 300th hit with the Mariners.
“That I was able to pull a hanging slider just shows that I was on time for a fastball,” France said. “That is the biggest key. If I can get on time for a fastball, I’m going to be in a good spot, and I feel like I’m getting there again.”
Kirby (3-3) got the win, while Jaime Barria (1-2) was tagged with the loss. Erik Swanson pitched the ninth for his third save.
It was Kirby’s second victory since being recalled from triple-A Tacoma on July 23. The Mariners optioned him down on July 9 to limit the rookie’s workload.
“He’s looked great,” Seattle manager Scott Servais said. “After we shut him down and gave him a little breather, he has come back and has thrown very well. The velo is still there, the secondary stuff is there, and he has looked strong. That is exactly what we need out of him going forward.”
This story originally appeared in Los Angeles Times.