Hisashi Iwakuma will make his final start before the All-Star break against the A's on Saturday and is coming off his second straight strong start after seven scoreless innings and 10 strikeouts in a 2-0 win against the Twins.
The 33-year-old Japanese standout missed the first month of the season with a torn finger tendon, but he is 7-4 with a 3.07 ERA in 13 starts since returning. Iwakuma appears to be back on track after two rough outings in late June.
"He threw the ball extremely well," manager Lloyd McClendon said. "I think he built off his last start and it was a pretty impressive outing for him. He pounded the strike zone very well."
Iwakuma, who finished third in the voting for last season's American League Cy Young Award, has allowed just one run in 13 innings over his last two outings after overcoming a lingering neck injury.
"Physically I'm feeling very good right now," Iwakuma said through translator Antony Suzuki. "My arm feels a lot better. I'm keeping the ball down and moving it to both sides of the plate, [which has] has helped me a lot. I have no pain or discomfort in my neck anymore, so that's something we don't have to worry about."
"He definitely looked like he was 100 percent and felt comfortable," catcher Mike Zunino said of Iwakuma's last start. "That was the best I've seen him. He's done a good job of fighting through some stuff and getting his rhythm and hopefully he can just keep building on that."
Iwakuma is 3-4 with a 4.35 ERA in seven games (six starts) against the A's, but this will be his first time pitching against them this season.
A's: Chavez looks to continue success against Mariners
A's starter Jesse Chavez is no stranger to the Mariners, and for most of his career, he has owned them.
In 10 outings against the division rival, Chavez is 0-1 but has a 1.99 ERA. But for most of his career, Chavez has been a reliever, and most of his outings against Seattle have come after he's jogged out from the bullpen.
His two career starts against the Mariners have both come this season, and they have been a mixed bag.
In his first outing -- the first start of his Major League career -- he picked up a quality start, going six innings while giving up only two runs (one earned).
His most recent outing against them, though, was not as good. He went 5 2/3 innings, but this time, he gave up four runs.
Mariners: McClendon not downplaying series
Though McClendon was hesitant to put too much emphasis on facing the first-place A's earlier this week, the Mariners manager adjusted his rotation so his three veteran starters -- Felix Hernandez, Iwakuma and Chris Young -- would be lined up to face the division rival.
McClendon didn't try to undersell the importance of the series when asked before Friday's opener.
"Of course it is [a big series]," he said. "They're leading our division. I'm not crazy. But if you think I'm going to say this is the do-or-die series of the year, that's ridiculous. We'll play them one game at a time and hopefully we win the series. If we don't, it's not the end of the year, no."
"But I think it should be a fantastic series. It'll be right up our alley -- low scoring," McClendon said with a laugh.
• Seattle is the only team in the Major Leagues with seven relief pitchers who have appeared in 30 or more games, though the Mariners rank 13th in the Majors in total bullpen innings (267). Going into Friday's game, Fernando Rodney, Danny Farquhar and Charlie Furbush are tied for the team lead of 37 appearances.
None of the Mariners' relievers rank in the top 10 in the American League in appearances, but the A's have three, including league leader Luke Gregerson, who has appeared in 45 games entering Friday.
Adam Lichtenstein is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.