No, he's not adding a third driver or putting a 70 degree wedge in play. Instead, it's a more practical choice; he's going to add a 2-iron. As Golf World's Dave Shedloski reported, Mickelson feels like the club will give him the advantage he needs off the tee.
"I've been experimenting the last few weeks trying to get the right 2-iron that flies about 255 or so off the tee, which is kind of what I'm gunning for," Mickelson said. "I think this one is dialed in just about right. I hit it very well today, so I think it's going to be the mainstay. It'll be in for the U.S. Open."
Considering how narrow the fairways tend to be at the U.S. Open and what Graeme McDowell had to say about Congressional's current course conditions and setup, maybe it's a smart choice to bring a long iron for the week and take the standard diabolical USGA rough out of play.