WASHINGTON -- Jason Bay was in the original starting lineup for Thursday's game in D.C., which would have marked his first major league action since fracturing a rib April 23.

But Bay was scratched after becoming violently nauseous before the game. He believes the antibiotic he was taking for a sinus infection, not the illness he has been dealing with itself, caused the reaction that will likely delay his return until Friday at Yankee Stadium.

"I actually felt good," Bay said. "And then I got instantly sick. And lucky the doctor was here and said, 'What's going on?' And I said, 'I felt fine. All of a sudden I had this feeling. I didn't feel so well and ran to the bathroom.'

"I said I had a sinus infection and I'm taking an antibiotic. And he was like, 'You're not taking blah, blah, blah, are you?' And I was like, 'Actually, that's exactly what I'm taking.' He was like, 'It's a great medicine, but the No. 1 side effect for about half the people is [nausea].'

"So that actually made me feel better. Because I didn't feel sick. It was just all of a sudden it kind of came out. It was just an adverse reaction to the antibiotic I was taking, so hopefully I'll be fine tomorrow."