"I did the same thing last year to freshen my pitchers up and Felix had the best September of his career," McClendon said. "Everybody thought I was nuts when I did, and I'll do it again because it's the right thing to do."
Edgar Olmos will get the nod on Sunday afternoon against the White Sox, while Vidal Nuno will take the mound on Monday against the Astros instead of Hernandez. McClendon is still undecided on when Walker will be skipped.
"Ideally, you'd like to be able to freshen guys up twice during the course of the year," McClendon said. "For various reasons, with the injuries that we had, it wasn't possible."
The Mariners have been without left-hander James Paxton since late May when he went on the disabled list with a finger strain on his throwing hand. Paxton made a rehab start with Triple-A Tacoma on Friday night, but still remains days away from returning. Hisashi Iwakuma also missed part of the year on the DL, but returned to regular duty in early July.
That's meant Hernandez has not been able to take a start off this season, having tossed 167 innings already through 26 games. Last September, Hernandez posted a 1.66 ERA with 42 strikeouts, but he did not miss a start, as McClendon noted.
Hernandez had missed a September start in 2013, when he finished with a 3.04 ERA. He bounced back the next year to finish with a cumulative 2.14 ERA.
Nuno last started with the Mariners on Aug. 22 and has pitched only one inning since.
McClendon hopes the same results can help Montgomery, who holds a 4-6 record and 4.60 ERA. Montgomery has carried a 9.61 ERA in the month of August after he went through June and July with a 3.20 ERA.
Olmos has thrown 7 2/3 innings in relief this season, including 3 2/3 scoreless frames on Tuesday. He was called up from Tacoma -- where he started -- on Aug. 17 and has stuck with the team since.
"I want to give Monty a break and let him regroup a little bit," McClendon said. "And Olmos threw the ball really well in his long outing."
Greg Garno is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.