Phil Mickelson fired an astonishing ten birdies to move into a share of the lead alongside Vijay Singh at the BMW Championship, where Lee Westwood and Rory McIlroy were just one behind.
Five adrift of overnight leader Singh at the start of his penultimate round, Mickelson delighted the Crooked Stick spectators with a stunning 64 that lifted him to 16 under.
The 42 year old’s performance was all the more remarkable given that he was one over par after three holes.
Five birdies in the next six put him firmly on course and he picked up as many shots on the way home either side of a second bogey at 14.
"Certainly my game went south for a while, and I was trying to piece it back together," said Mickelson.
"It's taken me a little while, but I could tell last week that my game was back and I was ready to play at the highest level again."
Singh, seeking a first win in four years, looked set to take a slender advantage into the final day, only to record a fourth bogey of the day on the last.
Westwood produced a magical chip in at the tenth and birdied three of his last four to claim third position on 15 under.
The Englishman soon had company when McIlroy birdied the last, putting him ahead of Adam Scott, Robert Garrigus and Dustin Johnson.
"It wasn't the greatest ball-striking round out there that I've ever had, but I somehow managed to scrape it around in 69 and I’m still in with a chance," said McIlroy.
Tiger Woods was eighth on 13 under after a 71, with Graeme McDowell a shot further back.