Shortly after 3 p.m. yesterday, Phil Hughes walked into the bullpen at Yankee Stadium hoping to take the next step toward returning to the Yankees' starting rotation.

Minutes later, Hughes walked out discouraged and unsure of when he will pitch again.

Hughes cut the bullpen session short when he felt "deadness" in his right arm after throwing around 12 pitches. The Yankees planned on having Hughes meet with Dr. Christopher Ahmad, the team physician, before last night's game against the White Sox to map out the next step.

"It's something I'm worried about," Hughes said.

The 24-year-old went on the 15-day disabled list on April 15 after he struggled through his first three starts with reduced velocity. Both Hughes and the Yankees have said they do not believe the right-hander is injured, and as of 5 last night, he had not undergone an MRI exam.

When the Yankees placed Hughes on the DL, they said they hoped he would be able to use the time off to rebuild his arm strength through a number of long-toss and bullpen sessions. Hughes made about 90 throws Saturday in Baltimore and was encouraged. The plan was for Hughes to make a minor league rehabilitation start Thursday if yesterday's session went well. Instead, the Yankees are left wondering when Hughes will return.

"Because everything was going so well you were encouraged," manager Joe Girardi said. "Now this is a setback. You're not quite as encouraged as you were before."

Hughes played long toss in the outfield with bullpen catcher Roman Rodriguez yesterday afternoon with pitching coach Larry Rothschild and teammate CC Sabathia looking on. Hughes then took the mound in the bullpen, where he said the same problem that has been bothering him cropped up again after a few pitches.

Hughes said he does not feel pain, but it feels like his pitches have nothing on them. He likened it to the feeling you get in your leg if it gets hit hard and goes numb.