TAMPA, Fla. -- New York Yankees left-hander Andy Pettitte has a mild muscle strain in his throwing elbow and will not throw for a few days.

Pettitte skipped his exhibition start Friday against Pittsburgh after feeling tightness in his elbow while warming up.

"The treatment is a short stint of rest," Yankees general manager Brain Cashman said Saturday. "Probably within four days."

Pettitte initially felt a twinge during the second inning of a two-inning outing March 3 against Houston but did not leave the game. When he felt it again Friday about 20 pitches into his pregame warmup, he decided not to pitch.

"I'm just trying to be very cautious," Pettitte said. "Really not that much pain, more tightness. I could have pitched."

Pettitte, a 15-game winner and the 2001 AL championship series MVP, had an MRI exam Friday. The results were negative.

"I'm not going to play catch for the next couple days," he said. "I should be able to go after that."

Pettitte said he overthrew a four-seam fastball against the Astros when his arm got ahead of his body but the discomfort was minor. He gave up two runs and four hits in that game.

Meanwhile, reliever Ramiro Mendoza underwent a bone scan for ailing neck on Friday. The results were negative.

Mendoza experienced continuing neck stiffness when he tried to play catch Thursday. Cashman said Mendoza is day to day.