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Girardi said that the Yankees' discussion of recent sleep studies for high-level athletes was one factor in prompting the change.
"We just felt it made a lot of sense for a couple reasons; sleep and early work, so they're not doing early work at 7:30, 8 in the morning," Girardi said. "[If] you're a pitcher throwing a bullpen [session], I mean, that's just not normal.
"And if you're an infielder trying to do work on the back fields, they're soaking wet, and that didn't make sense. So we just felt, while we can do it ... let's do it, and it has worked out well."
Scott Kutscher, a clinical assistant professor at the Stanford Center for Sleep Sciences and Medicine, told The Wall Street Journal that early mornings in Spring Training make little sense because players are preparing for a season that consists of mostly night games.
"These are still young men whose primary job is a nighttime job," Kutscher told the newspaper. "So you want to get in line with how their bodies are going to respond and how you want to perform."
The Yankees' modified timetable can only last until Grapefruit League games begin, with New York set to host the Tigers on March 2 at 1:05 p.m. ET at George M. Steinbrenner Field. The necessary preparation for a game, even if it is an exhibition, must start earlier in the morning.
But for now, Girardi said that one of the first things he told pitchers and catchers was that arriving early to the clubhouse wouldn't impress him, strongly encouraging them to take advantage and sleep in a little later.
The position players will receive similar instructions, with Thursday's first full-squad workout outlined for a late-morning start.
"We may be five, 10 minutes late, because we have a meeting, but 11:30," Girardi said.