Posada was back behind the plate for Saturday's game against the Blue Jays and batting sixth in the lineup. He said he will wear a plastic brace in the field underneath his glove to protect the thumb.
Posada took a foul tip off the thumb on his non-throwing hand in Wednesday's 4-2 victory against the Mariners, prompting manager Joe Girardi to sit him on both Thursday and Friday. Girardi said he left Posada out of the lineup primarily for precautionary reasons.
Posada is not 100 percent, but Girardi deemed him healthy enough to play, though the manager is concerned about the possibility of another foul tip. He watched Posada take batting practice and was confident he was ready to go.
"He could injure it further, but I don't think to a greater extent," Girardi said. "If he gets hit again today, it's going to hurt. It's going to hurt for a couple more days. That's the thing. We could probably leave him out three of four days, he could get hit Tuesday or Wednesday, and it's going to come back. He got hit on a freak play, and you hope we don't have another freak play."
Jared Diamond is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.