But with Kevin Millwood returning to the rotation this weekend and Erasmo Ramirez potentially coming back from the disabled list in time to start after the All-Star break, Iwakuma won't be in line for another spot start unless something goes wrong, it appears.
"We're OK now," manager Eric Wedge said Tuesday. "We don't have to worry about it until after the break, really. He'll be available for us this weekend [in the bullpen]. Let's see how Ramirez comes back. We've got time now. Between the off-day and the break, we don't have to make any decisions until afterward."
Millwood will start Friday in Oakland after being pushed back four days due to a sore groin. Ramirez is on the disabled list with a strained elbow, but is eligible to return by July 16. With the All-Star break, the Mariners won't need their fourth and fifth starters again until July 16 and 17 in Kansas City.
Iwakuma had been pitching in long relief for the Mariners up until Monday, but was always a starter in Japan. He's been improving steadily since Spring Training as he adjusts to the Major Leagues and gains strength from a shoulder injury that hampered him in 2011.
"My velocity is better than Spring Training, obviously, and my breaking balls are moving better," Iwakuma said through translator Daisuke Sekiba. "It feels better right now to pitch."