"I'm not sure," Yankees manager Joe Girardi said. "He was really sick tonight. I watched him take BP, and he just didn't have that normal Derek Jeter energy. That was a real concern of mine."
While he was coughing at his locker on Friday before the Yankees' 9-1 victory, Jeter played coy through a congested voice, telling reporters that he felt "great" and that he would be "good" to play.
Asked how long he'd had the cough, Jeter replied, "For parts of 35 years."
But Girardi said that Jeter's cough is the worst one on a Yankees club that has battled illness recently, perhaps exacerbated by sharing close quarters on a charter flight to New York from Atlanta on Thursday.
Melky Cabrera and Hideki Matsui are beginning to recover from flu-like symptoms, but now Jeter and Robinson Cano have started coughing and feeling under the weather. Girardi said that Jeter developed a fever and relaxed for most of Friday's game.
"We were fortunate we were able to rest him all night, and he stayed in the clubhouse all night," Girardi said. "It was nice not having to use him and run his energy level down."
Jeter said he inspected the field at Citi Field and said he could only imagine it was better than its predecessor, the dated Shea Stadium, which was bulldozed to make room for parking at the new facility.
But Jeter had his days to remember at Shea, particularly the 2000 World Series, which included a leadoff home run on Bobby Jones' first pitch during Game 4.
"The Subway Series was probably my biggest memory," Jeter said. "You have some good memories over there, but I'm sure there aren't too many players who miss it."
Girardi said it was difficult to believe that Jeter, who made his Major League debut in 1996, was spending his Friday celebrating birthday No. 35.
"He won't admit to that, so if I ask him, he's going to tell me he's 25," Girardi said. "It's hard to believe. Sometimes I look at these guys and I still think of them as kids, because that's what they were when I played with them. Andy [Pettitte] is the same thing. It's hard to believe they're that old."
Friday marked the first time in Jeter's career since Interleague Play began in 1997 that he did not play against the Mets. The only other time that Jeter did not start was on May 22, 2005, one day after he was drilled in the left elbow by a Kris Benson pitch.
Replaced at shortstop by Rey Sanchez, Jeter eventually appeared as a pinch-runner in the eighth inning that afternoon and scored a run as the Yankees defeated the Mets, 5-3.