In his first season as Yankees manager, Girardi sat out Friday night and Saturday because of an upper respiratory infection. Bench coach Rob Thomson managed the team in Girardi's place, and New York lost both games to Tampa Bay.
"I'm better than I was. I don't have the fever I had the last couple days, so that's a good thing," Girardi said before Sunday's game.
Girardi stayed in his office during the games Friday and Saturday.
"They would run back and forth and we'd talk about things," he said. "It's not the same feeling as being on the bench. It's hard. It's not something I enjoyed and we had to find a way to get through it. I'm glad I'm back."
Girardi said Giambi is day to day and could be available off the bench if necessary.
"I'll talk to him after he's had some treatment," Girardi said. "Just watching it on TV, I told him, 'It looked like you were 12 years old again.' He was actually thinking of going to third base. To me, he's feeling pretty good, but he maybe overdid it a little bit."
Girardi said he didn't think Giambi would need to go on the disabled list.