But Walker, who is 2-2 with a 1.97 ERA in six starts, reiterated Saturday that the situation was minor, just a sore neck caused from sleeping wrong on Thursday night.
"I've had it before, I'm sure everyone has," he said. "It's just from sleeping. It's still a little sore, definitely, but it feels a lot better."
The Mariners' training staff tried to get Walker loosened up prior to the game, but he still couldn't turn his head once the game began and said as a result he felt like he was throwing with just his arm instead of his full body.
"I was really hoping it would loosen up once the game started," he said. "It did a little bit, but not enough."
Walker said if things feel fully normal, he'll throw his usual between-starts bullpen session on Sunday. If not, he'll wait until Monday. And in a worst-case scenario, he'd just skip the bullpen, throw a flat-ground session on Tuesday and be ready for his start on Wednesday.
"I'll be ready in five days," he said.
The youngster has been Seattle's best starter over the first month in a rotation that has the second-best ERA of any group in the American League at 3.38, trailing only the White Sox mark of 3.31 going into Saturday's games.
Manager Scott Servais said his rotation has been the backbone of the team's early success.
"We've been very fortunate," Servais said prior to Saturday's game with the Astros. "Last night was the hiccup when I had to go really early in the game to get somebody else in there and try to piece it together. But that's the key to putting good streaks together. It's always driven by starting pitching, guys that keep you in the game every night and you hope your offense responds. Which we have, just last night wasn't one of those nights."
• Outfielder Franklin Gutierrez was in the lineup Saturday for just the second time in the past 10 days, but Servais said that has been the result of a long run of facing right-handed starters and not an issue of health.
"He's been fine," Servais said. "We've got the lefty string now. We've got [Dallas] Keuchel tonight, and it looks like the first two against Tampa will be left-handed. So three of the next four days, he and Dae-Ho Lee will be in there and hopefully get something going there. Guti is ready to go, he just hasn't had a lot of opportunities."
• First baseman Adam Lind is 2-for-15 on the current road trip and his slash line sits on .210/.235/.272 in 25 games. Servais said the 32-year-old has been chasing too many pitches out of the zone as he's tried to get going.
"He's been in here early the last couple days," Servais said. "Adam is about as care-free as anybody, but he knows he needs to get it going. He's trying to make adjustments. When you swing at that many pitches out of the strike zone, your timing is late. You're late getting to the hitting position. That's what he's working on with Edgar [Martinez]. He's trying to get there early enough to recognize the fastball, breaking ball and balls and strikes. That's what good hitters do. He'll figure it out."