"As I speak now, he will not miss a start," McClendon said.
Iwakuma felt some tightness prior to his last outing Sunday, and he said he wasn't sure he was going to be able to pitch that day until trainers worked on his neck while he was warming up before the game.
But the 33-year-old Iwakuma went eight innings and allowed just one run on six hits, while throwing 106 pitches in a 5-1 victory over the Rangers.
Iwakuma missed the first month of the season with a torn tendon in his right middle finger, but he has gone 5-3 with a 2.59 ERA in nine starts since his return. He's scheduled to face Royals standout right-hander James Shields on Friday.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.