The Englishman's seven-under-par opening round gave him a one-stroke clubhouse lead over the morning wave of starters in Tennessee, with American Casey Wittenberg back home in six under and Ireland's Padraig Harrington third following a 65.
That left three-time major winner Harrington a shot clear of an eight-man group in the clubhouse at four under par.
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Hide AdWestwood, who played next week's US Open venue Pebble Beach on Sunday and Monday ahead of the second major of the year, hit the ground running. He went bogey-free with five birdies and an eagle, going out in 29 for his opening nine holes, starting from the 10th tee, with his eagle 3 coming at the par-5 16th.
Westwood added his fifth and final birdie of the round before carding pars all the way home – the only blemish was missing a short birdie putt at the ninth, his last.
England's Greg Owen had an opening one-under 69.