From the official site:

... Rodriguez, the Major Leagues' leading vote-getter for the July 10 All-Star Game at San Francisco, revealed Friday that he has no intention of participating in this year's Home Run Derby.

"I've never been good at it, No. 1," Rodriguez said. "I'm going to enjoy watching it this year. I'll have a good seat. I've worked hard for my swing and I definitely don't want to let anything get in the way of it. My only responsibility this year is to the New York Yankees."