This was the latest in a string of similar injuries for the Milwaukee second baseman, who had surgery to repair the area around a tendon in his wrist in 2006 and played in pain for much of 2007. The injuries have been largely cited for Weeks' struggles at the plate, including a career batting average of .244.
"His bat is so quick, and I think that definitely has something to do with it," Yost said of the recurring injuries.
Weeks was removed on Sunday after striking out against Los Angeles Dodgers lefty Clatyon Kershaw.
"It's just sore," Weeks said. "The bat slipped out of my hand, and I just followed through with my bottom hand and put pressure on my thumb. It's a little sore, but it's fine."
None of the switch-hitting Ray Durham's nine starts since joining the Brewers in July have come against a left-handed pitcher. The veteran is hitting just .214 and slugging .314 against southpaws this season, compared to .297 and .432 against right-handed pitchers.
Should Weeks be forced to miss any length of time, it would foil Yost's plan to use Durham 2-3 times per week. The Brewers skipper discussed the situation with Durham's former manager, San Francisco's Bruce Bochy, who advised Yost to use Durham less frequently with the 36-year-old nursing troubling hamstrings.
Meanwhile, closer Salomon Torres, who left his Saturday outing with groin tightness, declared himself available despite the lingering nuisance.
"There's a little tightness there, but we've been working on it," Torres said. "Yesterday, I was available in an emergency and today, I'm good to go."
Torres said he had been experiencing the discomfort for a while.
"We've been taking preventive measures," he said. "I've been stretching, working on the treadmill and doing all the necessary things in order to continue. It'll get better, and it's not a big concern."
Weeks saw Dr. William Raasch after batting practice, and he confirmed the diagnosis of a left thumb sprain and re-affirmed the day-to-day prognosis.