Remember when people wondered if Merion would be able to stand up to the modern player? Turns out there was nothing to worry about. This year's U.S. Open course played the toughest on tour with an average score of 4.546 shots over par. In fact, the four major championship venues came in Nos. 1-4, with Muirfield (+3.478), Oak Hill (+1.996) and Augusta National (+1.318) following Merion.