"He's still being examined," Astros general manager James Click said Thursday, one day before Houston hosts the Boston Red Sox in Game 1. "Just going to keep looking at him, see how he is."
McCullers left Game 4 of the ALDS against the Chicago White Sox on Tuesday with forearm tightness but didn't think at the time that the injury was serious.
"I just started getting tight at the beginning of the inning," McCullers said after the game. "I just told them, 'Listen, I'm not 100 percent.'"
Houston has until 10 a.m. local time Friday to set its ALCS roster.
"Any time you have a pitcher come out with forearm anything, you want to take your precautions and make sure you know exactly what's going on," Click said.
Astros manager Dusty Baker indicated that McCuller's roster spot could be filled by veteran right-hander Jake Odorizzi, who was left off the roster for the ALDS.
"I know that I've worked really hard to be able to have the results that I have and be able to have the performances that I have, and it means a lot that they have the confidence in me to be a starter for tomorrow [Friday]," Valdez said through an interpreter.
The outlook for outfielder Jake Meyers is a little better, as he took to the practice field Thursday for the first time since injuring his left shoulder in Game 4 while attempting to make a leaping catch at the wall.
"I'm feeling good," Meyers said. "I'm feeling a lot better -- doing rehab and stuff like that to get it stronger."
Asked whether he would be available to play if needed, Meyers answered "yes."
As with McCullers, however, Baker was holding off on any roster decision on Meyers.
"We're not sure about that either," Baker said. "I've got to talk to the trainers afterwards, see how he came out of it today [Thursday]."
Sale said he was anxious to return to the mound after giving up five runs in one inning of work in his last appearance.
"I appreciate that," Sale said. "I don't take that lightly. You know, there's no hiding from it, no secret. I've been absolutely horrible. Probably my two worst starts of my career back-to-back leading up to this."