Recovered from a finger injury and riding a 23-inning scoreless stretch, Iwakuma takes the mound against the Houston Astros on Saturday night at Minute Maid Park.
Iwakuma earned his first All-Star nod and finished third in the AL Cy Young award voting last season when he went 14-6 with a 2.66 ERA in 33 starts. The right-hander didn't allow a run in four of his final five outings, and none over the last three during which he yielded 11 hits.
However, the 33-year-old Iwakuma has had to wait to build on that stellar finish after he sprained a tendon in his middle finger while catching it in some netting during spring training.
"I look forward to (Saturday)," he told the Mariners' official website. "It's been a long wait. I've always wanted to be part of the team soon and contribute, so that said, it's a very exciting day for me."
Manager Lloyd McClendon is happy to have Iwakuma again following ace Felix Hernandez, who allowed two earned runs and five hits in five innings while dealing with flu-like symptoms during Friday's 5-4, 11-inning loss to the Astros (10-19).
"Anytime you can go back-to-back All-Star pitchers in your rotation, that's pretty good," McClendon said.
Iwakuma went 2-1 with a 1.38 ERA in four starts against the Astros last season.
He'll try to help the Mariners (12-15) bounce back from blowing a one-run, eighth-inning lead and losing for the second time in seven games since dropping eight in a row.
George Springer chopped a bases-loaded single over the head of Seattle third baseman Kyle Seager with the bases loaded in the 11th on Friday to help the Astros improve to 3-4 on a nine-game homestand. Springer hit .121 in his previous nine games and was hitless with four strikeouts in his first five at-bats Friday.
"When you watch George, and even through his struggles (Friday), there was never a doubt in his mind," manager Bo Porter said. ''He continues to battle."
Jose Altuve had three hits for Houston, which has won seven of eight versus Seattle. Altuve is batting .394 (13 or 33) on the homestand and is 6 for 9 in his last two home games against the Mariners.
He went 4 for 11 with a double versus Iwakuma in 2013.
Scheduled Houston starter Dallas Keuchel (2-1, 3.56 ERA) allowed four runs in five innings of a season-opening 5-1 loss to the Los Angeles Angels, but has gone 2-0 with a 2.84 ERA in the next four. That included a two-run, eight-strikeout effort over six innings in a 7-2 victory at Seattle on April 21.
Keuchel, 1-2 with a 2.84 ERA as a starter against the Mariners, gave up three runs in 6 1-3 innings while not factoring in the decision of a 7-6 win over Oakland last Saturday.
"He's probably pitching the best he's pitched in his career," Porter told the Astros' official website.
Seattle's Corey Hart is 3 for 9 with two homers versus Keuchel, but 2 for 21 in his last six games after going 11 for 27 (.407) in his previous seven.