Iwakuma has missed two starts since straining the lat muscle behind his right shoulder and going on the 15-day DL, while Wilhelmsen has been sidelined since April 11 with a hyperextended right elbow.
Wilhelmsen is closer to returning as he threw 25 pitches off a mound on Friday for the first time since his injury. He'll throw another bullpen session on Sunday before it's determined if he's ready to go out on a Minor League rehab. If all goes well, he should be ready to rejoin the club in mid-May.
The 31-year-old reliever said he threw fastballs and sinkers at about 90-95 percent on Friday and "felt great. No issues at all."
Wilhelmsen has been out longer than initially expected, but says he's progressing fine now.
"The first few times I played catch, my shoulder felt a little cranky," he said. "But that was just due to not doing anything physically with it for awhile. After we got out to 100 feet, it loosened up and there have been no problems for the last week or so."
Iwakuma, who remained behind in Seattle to rehab during the current 10-game road trip, is just beginning the process of starting to play catch. The 2013 All-Star was 0-1 with a 6.61 ERA in his first three starts before reporting soreness behind his shoulder.
With Iwakuma expected to miss most of May, left-hander Roenis Elias made his second start in his place on Friday against the Astros.
• Veteran left-hander Joe Saunders opted out of his Minor League contract with the Mariners to become a free agent on Friday. Working as a reliever for Triple-A Tacoma, Saunders had gone 0-3 with a 5.73 ERA over 11 innings in six appearances. The 33-year-old pitched 10 seasons in the Majors with career marks of 89-86, 4.37 ERA in 235 games (229 starts). He was 11-16 with a 5.26 ERA in 32 starts for Seattle in 2013, then split last year between the Rangers and Orioles.
• Second baseman Robinson Cano finished April going 2-for-22 in his last five games as his average dropped from .304 to .253, but McClendon said he's not worried about the six-time All-Star with a .309 career average.
"He's working at it," McClendon said before Friday's game. "He's in a little funk now, but Robbie has a tremendous track record. I think when it's all said and done, his numbers will be right where they're supposed to be. We went through this last year and had this same conversation. He's going to hit. He's going to be just fine."
• On the flip side, Nelson Cruz finished his first month with the Mariners batting .322 while leading the American League with a .724 slugging percentage. Cruz finished the month tied with Boston's Hanley Ramirez for the Major League lead in home runs (10) and RBIs (22) and second to the Dodgers' Adrian Gonzalez (.790) in slugging percentage. He also led MLB with five game-winning RBIs.