As one of the earlier starters in round two, Spieth was held up Friday when heavy rain forced a brief suspension in play at Baltusrol Golf Club in New Jersey.
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Spieth moved to within one stroke of overnight leader Jimmy Walker with birdies at the 10th, his first hole, 11th, 13th, 17th and 18th offsetting a solitary bogey on the 12th.
Spieth was birdie-free for much of the first day, but he picked up two shots in his final three holes to open the tournament with an even-par 70.
Patrick Reed and Webb Simpson moved into the group at 3 under, one behind Spieth.
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Martin Kaymer, who began the day one off the pace in second alongside Ross Fisher and Emiliano Grillo, slipped back to 2 under through 11 holes.
British Open winner Henrik Stenson was also 2 over at one point in his round and 1 under overall but eagled No. 18 to move back to 3 under as he made the turn.
U.S. Open champion Dustin Johnson appeared certain to miss the cut after losing further ground on the back of his first-round 77.
Walker, Fisher and Grillo were among Friday’s later starters.
Scoring at the PGA Championship
Once play ends, field will be reduced with the cut line likely 2-over par, although it could be 1 over.
