Ireland's Padraig Harrington shot a two-under-par 70 - six strokes off the lead - at the Memorial tournament in Columbus, Ohio.
The Dubliner enjoyed a run of four birdies in six holes between the second and seventh to complete the front nine in 32.
However, dropped shots in successive holes at the par-three 12th and par-four 13th saw him slip back into the chasing pack with a first round score of 70.
American Charles Howell's blistering 64 gave him the clubhouse lead at the end of the first round.
Luke Donald's round of 70 included three birdies and only one bogey - a five at the 401-yard third - while former European number one Lee Westwood had a real mixed round.
Birdies on the first and fifth had put him two under playing the ninth but a dropped shot on that par four was immediately recovered on the next hole, with a three on the 441-yard 10th.
However, a double-bogey five at the 12th spoiled all his previous good work and the Worksop golfer finished with a level-par 72.
Swede Jesper Parnevik carded a round of 70, while Spanish duo Jose Maria Olazabal and Sergio Garcia both shot one-over-par 73s.
Two-time US Masters winners Bernhard Langer had a day to forget with a seven-over-par 79 which included three double-bogeys in his first nine holes, four other dropped shots, and three birdies to leave him 103rd in a field of 104.
PA