Victor Dubuisson carded an eagle and seven birdies in his 64 to finish 13 under par, a shot ahead of Fitzpatrick, Nicolas Colsaerts and Tyrrell Hatton, with Rafa Cabrera Bello, Lee Westwood and Francesco Molinari another stroke adrift.
On a day of low scoring, Colsaerts – who has not won on the European Tour since 2012 – fired six birdies and two eagles in his 66, but the best round of the day, and week, came from Cabrera Bello.
The world number 30, who was unbeaten on his Ryder Cup debut at Hazeltine, surged through the field with a superb 63 containing 10 birdies and a solitary bogey on the ninth.
Rory McIlroy fared even worse on the last after finding water with his approach, the resulting bogey leaving the defending champion to sign for a second consecutive 68 and eight-shot deficit.
Open champion Henrik Stenson remains on course to win the Race to Dubai after a 70 left him alongside McIlroy on five under, with nearest rival Danny Willett one over after a 76.
Alex Noren, who can deny fellow Swede Stenson the title by finishing in the top two, is in a tie for 13th after carding a 69 in pursuit of an incredible fifth win in 12 events.
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