But the Mariners pitcher said he wasn't satisfied with his second Minor League rehab start of the season, as he fell short of his target of five innings, allowing three hits and one walk and striking out four in a 68-pitch, 47-strike outing for Triple-A Tacoma -- which defeated the Reno Aces, 1-0, in 10 innings.
Iwakuma, who was placed on the disabled list April 24 with a strained right latissimus dorsi muscle, worked through some early mechanical issues -- including his shoulder flying open in the first two innings -- but ended his night with better command.
"I had to fight some mechanics, but I was able to get some of the balls down," Iwakuma said through interpreter Antony Suzuki. "Some of the balls I left up in the zone, as you saw, but overall I thought I had good arm speed and arm action, so I think I'm going in the right direction."
The 34-year-old right-hander struck out two in a 19-pitch first inning, the only hit against him coming on a double down the left-field line by second baseman Brandon Drury.
He again allowed just one hit in each of his next two innings -- a single to right-center off the bat of shortstop Michael Freeman in the second, followed by an infield single by left fielder Nick Buss in the third -- but managed to work out of both innings without allowing Reno to score.
The Aces' primary effect on Iwakuma through three innings wasn't on the scoreboard but on his pitch count. Deep counts to several hitters quickly brought Iwakuma's pitch total to 60 after three innings.
"With the fastball and the split, everything was flying open and it tails to the arm side, and that's what I had to work on today to make adjustments," Iwakuma said.
Iwakuma's last inning showed the fruit of those adjustments. He retired the Aces in order in the fourth without reaching a two-ball count. He also managed to hold his fastball velocity close to 90-mph throughout.
"I'm not a power pitcher, as you guys all know," Iwakuma said. "I'm more about throwing a crisp, sharp fastball -- and the harder, the better, obviously -- but I'm not worried about speed. I mean 88 to 91 is pretty much standard for me."
In his first rehab start with the Class A Short Season Everett AquaSox on Saturday night, Iwakuma lasted 3 2/3 innings and gave up one run on three hits while throwing 56 pitches. Mariners manager Lloyd McClendon said Sunday he would like Iwakuma to start at least two times for Tacoma prior to rejoining the Mariners.
When asked how close he is to being Major League-ready, Iwakuma said he has a few things to tweak but is not far off.
"I need to make some adjustments, but mentally I'm ready to go," Iwakuma said. "If they call me up, I'll be ready to play."