Another day, another Yankee off to the disabled list.
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"We don't think it's overly serious,'' Cashman said, "but we want to play it safe.''
Lefty Vidal Nuño, who pitched five shutout innings in the first major-league start of his career Monday in Cleveland, will be called up from Triple-A Scranton/Wilkes-Barre.
Cashman said Nuño, 25, could take Pettitte's next scheduled start in the rotation, Tuesday in Baltimore, or could be slotted in sooner to give someone else an extra day's rest.
The Yankees, who got Curtis Granderson back earlier in the week, have 11 players on the DL.
Pettitte, 40, was scratched from his April 14 start because of lower-back spasms, but neither he nor Cashman believes that problem relates to this one.
Pettitte "locked up'' in the fourth inning during Thursday's start, a sensation that dissipated. But it occurred again in the fifth, and after Pettitte struck out the first two batters, Joe Girardi removed him. Pettitte argued to stay in the game and found himself arguing again Friday against the DL stint.
"I think it could be overly cautious but I also understand,'' he said. "I understand that I probably need a few days to let it calm down before I can throw a bullpen. I need to pitch on Tuesday and they don't want to send me out there in Baltimore and I start warming up and it locks up and then we don't have pitching. I understand that it's early and everyone wants to play it safe. But it's disappointing. I want to take my turn every fifth day.''
Pettitte, who is 4-3 with a 3.83 ERA, said his expectation going into the year was to do that throughout the season, but Cashman said he anticipated this kind of setback.
"This is the safe play,'' Cashman said. "I didn't expect him to give us 200 innings this year regardless. Thankfully, it's minor.''
Pettitte said he expects to return when his 15 days are up.
"I had high expectations for this season, especially pitching a full season,'' he said. "Now this is a bump in the road and I want to get everything right and not have anything go wrong the rest of the way and hopefully give us a great rest of the season.''