CLEARWATER, Fla. -- Eduardo Nunez went 3-for-3 on Tuesday, but not in a stat category that would show up in any box score. The Yankees infielder just can't seem to keep his helmet on his head.

Each time he ran down the line during three groundouts in the Yanks' 4-3 loss to the Phillies at Bright House Field, the batting helmet popped off Nunez's head, bouncing to the dirt before Nunez made it the full 90 feet to first base.

It has been a recurring problem for Nunez, and it hasn't escaped the attention of his teammates.

"They're all over me," Nunez said, giggling. "They kill me, especially [Derek] Jeter: "Nuney, what's wrong with you? This is the Yankees. We can't do that here."

Nunez can't figure out the issue since he is still wearing the same size helmet as last year, a 7 1/4 model.

"Man, I don't know how it happens," Nunez said. "This helmet fits me good on my head. You know, it's tight! I don't know what the problem is."

Major League Baseball introduced new mandatory Rawlings S100 Pro Comp helmets this spring, which are designed to withstand baseball impacts of 100 mph.

Perhaps that could be one possible explanation, but then again, there has been no rash of MLB players losing their helmets around other big league camps.

"It's Nuney," manager Joe Girardi said. "That's the easiest way to describe that, right?"