Upton said there was no doubt he would be ready for the series opener against New York, and his sprained left ankle felt "good enough to play on."
"That's all that matters. It's a big series," Upton said. "I told them yesterday, 'I'm playing tomorrow.' That was the plan all along."
Manager Joe Maddon said Upton wanted to play Thursday afternoon against the Tigers, but his lateral movement was still a little bit of a problem after he left Tuesday's game and sat out Wednesday's as well. Maddon added that he wasn't concerned about Upton's ankle Friday.
"You've got to keep a little bit of an eye on it, but I'd say if it's not 100 [percent], he's up in the 90s," Maddon said. "It's that back-of-your-mind kind of thing."
Zobrist, meanwhile, was still a little sore Friday, Maddon said. The utility man left Wednesday night's game with lower-back stiffness that he said was caused by taking too many aggressive swings in the batting cage.
Maddon said "it's a possibility" that Zobrist won't play at all against the Yankees, and the team should know by Sunday how serious the injury is. Maddon didn't think it was serious enough to consider putting Zobrist on the disabled list, though.
"He feels a lot better today than he did yesterday, so all the work they've been doing is paying off," Maddon said. "We'll see."