J.A. Happ has been up and down all season, and the frustration is getting to him.

The New York Yankees' veteran left-hander is 10-8 with a 5.58 ERA entering Monday night's scheduled start in the opener of a three-game series at Seattle.

"I know he's frustrated obviously," Yankees manager Aaron Boone told reporters. "We just have to keep grinding away. The stuff is there enough for him to go out and be successful. We have to continue to try and find a way with him."

Happ has alternated losses and wins in each of his past five starts, going 2-3 with a 7.01 ERA over that span. In his last outing Wednesday at Oakland, Happ allowed five runs on four hits in four innings of a 6-4 loss.

"I haven't struggled like this in a while," the 13-year veteran told reporters. "But again, I'm doing everything I can every day to come in and try to figure this thing out and support the rest of the guys. I feel good. I feel like I can make the adjustments. That's my hope at least."

Two of the four hits Happ allowed to the Athletics were home runs. He's allowed 31 homers in 25 starts this season, four more than his previous season high set in 2018.

"Struggling to keep the ball in the park for whatever reason," Happ said. "It's not for lack of trying to figure it out. We're trying to do everything we can between starts to figure out sequencing, location, execution, even delivery. But they got the two (homers Wednesday) and they had a guy on base each time, and that makes it tough."

The results have been perplexing for Happ, who went 17-6 with a 3.65 ERA a season ago, including 7-0 with a 2.69 ERA with the Yankees after being acquired from Toronto just before the trade deadline.

"I feel like I have the same stuff," Happ said. "It seems similar to me. So that's part of the process of trying to figure out why the results haven't been there."

A return to Seattle, where Happ spent half a season in 2015, might be the best tonic. Happ had perhaps his best start of the season May 9 at home against the Mariners, allowing one hit in five scoreless innings in a 3-1 victory. He's 5-2 with a 4.46 ERA in eight career starts against Seattle.

After being swept in a three-game series at Oakland to open their nine-game trip, the American League East-leading Yankees rebounded to take two of three games over the weekend against the Los Angeles Dodgers. That included a 5-1 victory Sunday night as right-hander Domingo German improved to 17-3 and the Bronx Bombers hit three homers, including one by Aaron Judge.

The Mariners, who are in last place in the AL West, have won each of their past four series and six of their past eight games. They defeated Toronto 3-1 Sunday, as Marco Gonzales pitched seven innings of one-run ball and utilityman Dylan Moore homered.

"It seems like every game we put him out there he does something," Mariners manager Scott Servais said of Moore. "It's a defensive play. It's a big hit. Though, I wasn't expecting a home run."

Seattle is scheduled to use a reliever as an opener before turning over the ball to left-hander Tommy Milone (3-7, 4.84 ERA), who has won his past two decisions. Milone is 0-2 with a 2.70 ERA in four career starts against the Yankees.

--Field Level Media