Manager Bo Porter's team, however, could be hard-pressed to get the best of him again at Safeco Field.
Looking to stay unbeaten at home, Iwakuma brings a 21 2-3 scoreless innings streak into Monday night's series opener against the Astros, who try to avoid a fifth consecutive loss.
Enjoying plenty of success in his second season since coming over from Japan, Iwakuma (6-1, 1.94 ERA) ranks third in the majors with a 6.08 strikeout-to-walk ratio and fourth in ERA. He's been even better at home, going 2-0 with a 1.08 ERA while striking out 38 and walking two over six starts spanning 41 2-3 innings.
Iwakuma uncharacteristically got into trouble during a 3-2 loss at Houston on April 23. The right-hander, who was dealing with a blister on his throwing hand at the time, struck out a season-high 11 but allowed all three runs, six hits and three walks in a season-low five innings.
Iwakuma, though, has since gone 4-0 over his last eight starts, allowing two runs or fewer in all but one of those outings. He turned in another superb performance Wednesday, yielding three hits over eight scoreless innings in a 7-5, 16-inning loss to the Chicago White Sox.
"He was in control the entire day and just did a fantastic job," manager Eric Wedge said. "I think when you talk about consistency with the delivery and stuff, he's done a fantastic job with that all year."
Iwakuma now turns his attention back to the Astros (22-42), who have scored five runs while going 3 for 28 with runners in scoring position during their skid. Houston went 0 for 7 in such situations Sunday in a 2-0 loss at Kansas City.
"We needed a couple of hits here and there," said first baseman Carlos Pena, who's mired in a 3-for-23 slump. "We aren't catching any breaks right now, but it'll come."
Houston will try to bounce back behind Dallas Keuchel (3-2, 4.70), who's looking to win a career-high third consecutive start. After allowing two runs in seven innings during a 6-3 road victory over the Los Angeles Angels on May 31, the left-hander yielded one run and five hits over six innings to beat Baltimore 11-7 on Wednesday.
"I thought Dallas did a good job," Porter said. "Even a couple of times when he did get in trouble, he made quality pitches to get out of the jams and hold their lineup at bay."
Keuchel will be making his first start against a Mariners team that's hit .214 while dropping four of five. Seattle (27-37) failed to get much going again and dropped a season-high 10 games under .500 with Sunday's 2-1 loss to the New York Yankees.
"We can't keep watching this. We've got to be better offensively," said Wedge, whose team is hitting a major league-worst .220 with runners in scoring position. "When we do create opportunities, we're not taking advantage of them."
Seattle has dropped nine of 11 to Houston, including four of six this year. Astros left fielder Chris Carter is 11 for 26 with four homers and six RBIs in those games, and he has four homers and eight RBIs in his last 10 overall.