SAN FRANCISCO — All it takes is one slight miss for this U.S. Open to get a whole lot harder.
    Tiger Woods pushed his tee shot on the 670-yard 16th hole at Olympic Club just enough to find the right rough, which was moist from the marine layer that covered the course Wednesday morning. The ball at least was sitting up, allowing him to take a cut with his 4-iron to get it back in play.
    It's rare when Woods cannot reach a par 5 in two shots.
    But having to smash a 3-wood from 256 yards for his third shot?
    In the days leading up to the U.S. Open, which begins today, the biggest debate was whether the toughest stretch at Olympic was the opening six holes, or all 18 of them. About the only consensus was there won't be a repeat of the score Rory McIlroy posted last year at Congressional — a record-shattering 16-under 268.
    Jack Nicklaus, an expert on the U.S. Open from having won four of them, was asked to name the toughest and easiest courses he has played in this championship. He finally settled on Pebble Beach in 1972, when the wind blew so hard that Nicklaus won by three shots at 2-over 290 and never broke 70.
    As for the easiest?
    As Nicklaus thought back to the 44 times he had played, USGA executive director Mike Davis playfully interrupted.
    "You didn't play last year, did you?" he said to Nicklaus.