Andrew Both reports:
"Even if it's soft I don't think anything close to even-par will win," Mickelson told reporters after firing a four-under 68 in the Wachovia Championship first round on Thursday.
"I think it's the hardest course in the world, 7,600 yards at sea level."
The 37-year-old Mickelson said the rough was particularly brutal, even by usual U.S. Open standards.
He played the course with two friends, both scratch-handicap amateurs.
"They are two very good amateurs and they shot about 85," said triple major winner Mickelson. "They had a better-ball score of 80."