SEATTLE -- Felix Hernandez has been scratched from his scheduled start Wednesday against the Astros as the Mariners ace continues to be hampered by what manager Eric Wedge called "a minor oblique strain" in his left side.
Hernandez will be replaced by rookie right-hander Brandon Maurer, who started 10 games at the beginning of the season and has been working in a long-relief role recently. Maurer, 23, is 4-7 with a 6.85 ERA.
Hernandez already had his start pushed back from Sunday after being removed from his previous outing on Sept. 2 in Kansas City after 6 2/3 innings upon feeling what was originally believed to be cramping in his lower back.
After the 26-year-old felt some stiffness again while throwing a flat-ground session on Saturday, the Mariners decided to delay his next start further rather than to push it at this point. The issue is not considered serious, but the club is being cautious with Hernandez, who has thrown 194 1/3 innings in 29 starts this season.
With 19 games remaining, Hernandez said he definitely will return this season, though it won't be until somewhere in the next road trip at the earliest. He'll throw another flat-ground session this weekend in St. Louis, then be re-evaluated.
"I will pitch [again]. I'm fine," Hernandez said. "Why would they shut me down? I've got to go out there and do my best. That's what I'm trying to do. We're trying to finish strong. We're trying to win as many games as we can."
But Wedge said the team would err on the side of caution if Hernandez doesn't feel 100 percent.
"I think we'll just have to really look closely at how he feels after he throws later in the week," Wedge said. "I think that'll be a good indicator for us of where we're at. He's been honest with us, which is huge. And he always has been, at least in my time here. We'll just see how he feels and go from there. We're not going to take any chances."
Hernandez is 12-9 with a 3.01 ERA and 200 strikeouts. He is currently third in the American League in strikeouts and fourth in innings pitched. The durable right-hander has thrown 200-plus innings in each of the past five years and this is his fifth consecutive season with 200 strikeouts. Wedge appreciates his desire to keep working.
"You want him to have that mentality," Wedge said. "He's conditioned for it. You've seen the innings that he's thrown before because he's conditioned for it. He's strong enough to handle it. If it's an injury, that's something that takes you away from that. But any competitor wants to finish what he started, anybody that competes the way he competes, you want to finish what you start."
The Mariners had already decided to go to a six-man rotation over the remaining weeks of the season to reduce the workload on all their pitchers. Rookie Taijuan Walker, who will make his third Major League start in Monday night's series opener against the Astros, will be shut down after that appearance.
Maurer was already slated to take Walker's place in the rotation the rest of the way. The club also is going with rookie James Paxton, who made his Major League debut on Saturday, along with Hisashi Iwakuma, Joe Saunders and Erasmo Ramirez.
Maurer has been used sporadically in long relief and has thrown just 1 1/3 innings in one appearance over the past 11 days, but said he's confident he can go as long as needed in a starting role.
"I'm excited. I'm ready to give it another go. I just didn't know when," said the youngster from California. "I think I can go 100 [pitches]. I feel good, so I will go until they tell me I can't go anymore. I feel about as fresh as I can right now."
Wedge said Hector Noesi will assume Maurer's long-relief role.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. Jacob Thorpe is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.