Walker, No. 5 on MLB.com's Top 100 Prospects list, said he understood McClendon's concern after he needed 83 pitches to get through a five-inning outing.
"Obviously I need to be better," Walker said. "I put a lot of pressure on myself to be better, too. I wasn't pleased with my start. So definitely, stuff like that is just motivation because I know I need to be better and they expect me to be better. I just take that as motivation and will take it into my next start."
Walker went 2-0 with a 2.70 ERA in his two recent starts for the Rainiers, but had just two strikeouts with four walks in 10 innings. He said his fastball command, which was a problem in his last start for Seattle when he walked five in four innings against the White Sox, is something he's found some answers for in recent bullpen sessions.
"Watching video from last year and this year, it's just my lower half, there's no drive and no legs in it," he said. "When I did use my legs, I was flying open. I didn't have a consistent release point. I worked on that in my last bullpen and felt different. I felt like I was able to explode and finish everything out front instead of side to side."
McClendon pondered giving Wednesday's start to reliever Tom Wilhelmsen, who has been stretched out up to four innings as a long man and made a spot start just before the All-Star break. But he said his bullpen "has been taxed" in recent days and moving Wilhelmsen out of that role didn't make sense.
"Obviously it still intrigues me about Wilhelmsen, but we just can't do it right now," McClendon said. "The Anaheim series was just too grueling for us. We're going to back off a little bit."
McClendon has indicated Wilhelmsen might be looked at in a starting role next spring, but he won't push to make that transition any sooner.
"I don't know what's going to happen three weeks from now, but as we speak now, that's not in the plans, no," he said.
Walker said he just wants to get on a consistent schedule now after an up-and-down first four months due to injury and his recent demotion.
"I definitely just want to get on a routine and just roll with it," he said. "It kind of sucks being out for a couple weeks, getting back and then shut down again, back up and down. It'd be nice to pitch well and start getting on a roll."
The Mariners will need to make a roster move to open a spot for Walker and likely will send Erasmo Ramirez back to Tacoma after his Tuesday night start against the Mets.