During manager Terry Francona's briefing with reporters on Tuesday he revealed Youkils went to Massachusetts General Hospital on Monday with what he thought may be kidney stones.
Instead, it was revealed Youkilis has lower back spasms, possibly tweaking his back in Sunday's 4-0 win over the Rays.
A team source said Youkilis did not stay overnight in the hospital and was with the team getting treatment. The Red Sox are hopeful it will only be a day or two before he's able to play again.
Francona also said catcher and first baseman Victor Martinez had left the team for personal reasons. He should return within the next few days.
Amy K. Nelson is a reporter for ESPNBoston.com.