Dustin Johnson produced a sensational final-hole eagle to establish a commanding five-shot lead heading into the final day of the Northern Trust.
The world number four capped a fine round by curling home a superb 40-foot putt on the 18th at TPC Boston.
It saw the 36-year-old follow up Friday’s 60 with a seven-under third-round 63 also featuring six birdies.
Johnson sits on 22 under, five ahead of fellow Americans Harris English, who shot five under, and Scottie Scheffler.
It is the largest 54-hole lead on the PGA Tour this season.
Scheffler’s 59 on Friday made him just the 12th player to shoot under 60 on the PGA Tour.
In his third round, he shot a four-under 67 including a birdie on the 18th, but he lost ground on overnight leader Johnson.
Tyrrell Hatton is the best-placed British player, with the English world number 14 sitting 10 shots behind Johnson despite an excellent eight-under 63.
Spanish world number one Jon Rahm is on 10 under. (BBC)