Iwakuma picked up the win in his last outing against the White Sox on Saturday, allowing seven hits and two runs in 5 2/3 innings in a 107-pitch performance. He'll now be pitching on seven days' rest, but McClendon said there were no health issues involved in the decision to push him back.
"Just giving him a couple extra days, that's all," he said.
As for the idea of going with an extra starter, McClendon wasn't biting.
"I'm trying to win games, as many as I can," he said.
Nuno has gone 0-2 with a 5.26 ERA in five starts since taking the opening created by J.A. Happ's trade to the Pirates on July 31. McClendon said he'll likely move Nuno back into the bullpen now and the lefty will available in relief starting Friday in Oakland.
That leaves Hernandez, Iwakuma, Taijuan Walker, Roenis Elias and Olmos as the current starters, with Mike Montgomery now pitching in Tacoma and Paxton set for one last rehab outing in Triple-A before he presumably replaces Olmos next week.
McClendon also needs to watch Walker's innings as he hits the final month of his first full year in the rotation, so further juggling is likely. The club does have four off-days in September, which also creates opportunities to push back or skip starts.
• Veteran left-hander Joe Beimel didn't fare well in his second rehab outing for Tacoma on Tuesday and likely won't be ready to rejoin the Mariners when he's eligible to come off the 15-day disabled list on Friday, as originally hoped. Beimel is recovering from shoulder fatigue.
"I was a little concerned about those numbers," McClendon said. "Hopefully he'll get to pitch one more time and we'll see. From a physical standpoint he's good. But you give up five hits and two runs in two-thirds of an inning, that's not very good."
• When reliever Logan Kensing picked up the victory in Tuesday's 7-5 decision over the Astros, it was the 33-year-old's first Major League win since Oct. 4, 2009, when he was with the Nationals, a gap of 2,158 days between victories.
• The Mariners have scheduled a second "Bark at the Park" day for Tuesday, Sept. 29, against the Astros at Safeco Field. Those interested in bringing their dog to the game can get information at mariners.com/bark.