Pierzynski rolled his left ankle in Monday's game in Bradenton, Fla., re-aggravating an injury that had troubled him earlier in camp.
And Ross, originally supposed to start Tuesday's game, was scratched because of left foot soreness.
"It was bothering me in the offseason. It got a little better, but as I was running … it's one of those things where I can run straight, but I can't really turn really good," Ross said. "The ligament in there has been kind of aggravated. I've been running funny on my foot."
Manager John Farrell said that Ross should be behind the plate again on Friday.
"They told me to hold off today, but it feels 100 percent today," said Ross. "I'll probably hit and throw tomorrow and hopefully Thursday and Friday I'll be in the game."
Pierzynski isn't scheduled to play Wednesday or Thursday, so he could also be back by Friday.
"He's got a little bit of swelling in there today but this is a couple, three days maybe before he's back behind the plate," said Farrell. "The one thing is it's twice in camp that it's happened so we have to be a little more cautious right now."