Lahiri, who shot a superb five-under 67 in the second round went up-and-down throughout his the day with five birdies, four bogeys and one double bogey.
Lahiri, who was three-under and tied 59th at the end of the second round dropped to tied 68th as top 70 and ties made the 54-hole cut, which was applied as more than 78 players made it past the 36-hole cut yesterday.
Brooks Koepka overcame two early bogeys and a sea of Jordan Spieth bobbleheads to shoot a five-under 65 and matching the AT&T Byron Nelson's best 54-hole score at 16-under 194. He moved into a two-stroke lead over Spieth going into the final round when they will be paired together again.
Lahiri called his round a "tale of two nines".
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"I got off to a horror start (with a double bogey on 11th after starting from 10th). Then I then tried to force the issue. It backfired badly on me," he said.
Spieth played his first PGA TOUR event at the AT&T Byron Nelson as a 16-year-old amateur six years ago. Ane, he is now the World No. 2 ranked player and his image is everywhere at TPC Four Seasons, including those bobbleheads.
Playing in the final threesome with Spieth and second-round leader Ben Crane, Koepka hit his first drive way left on the way to an opening bogey. There were birdies at No. 3 and 5, but Koepka followed with another bogey at No. 6 when he hit his first two shots into the rough.
Matt Kuchar (65), Bud Cauley (68) and Sergio Garcia (68) were tied for third at 13-under. Crane, who turned 40 in March, shot 72 and dropped to 10-under and in a tie for 11th.