Lee Westwood made 11 birdies to shoot a 61 on Saturday and grab a share of the lead with struggling Louis Oosthuizen after the third round of the HSBC Champions.
Oosthuizen, the 2010 British Open champion, came into the weekend with a five-stroke lead over the field, but struggled with his putting and carded a 70.
The South African had a chance to retake the lead with a 15-foot birdie putt on the 18th hole, but missed by inches-the last of many near misses throughout the day.
Westwood and Oosthuizen are level at 18-under going into Sunday, three shots ahead of Phil Mickelson, who made seven birdies en route to a 66.
Ernie Els briefly surged into a share of the lead on the back nine before dumping his ball into a reservoir on the tricky 15th hole and taking a double bogey. He shot a 69 to drop to fourth place, level with Bill Haas (66) and Ian Poulter (65).
It was the second time in three weeks Westwood shot a 61-he also had one to beat Charl Schwartzel in the semifinals of the World Golf Final exhibition in Turkey in mid-October.
But as good as his score was Saturday, it wasn't even the low round of the day. That belonged to American Brandt Snedeker, who had a chance to shoot golf's magical 59 but missed a 15-foot putt for birdie on the 18th hole. He finished with a 60, a new course record.
Starting the day back in 12th place, Westwood began his assault on the leaderboard with three consecutive birdies on the first three holes Saturday.
He then birdied the fifth and seventh holes and sunk a 10-foot putt for another birdie on the 573-yard par-5 ninth hole to make the turn at 13 under, four strokes back. The Englishman kept up the pressure on the back nine, closing his round with four more birdies to catch Oosthuizen and Els.
After two rounds of nearly flawless golf, Oosthuizen was five strokes up on the field and looked to be comfortably in control going into the weekend. The South African's two-round score of 16-under 128 was the lowest through 36 holes at any World Golf Championship event since they began in 1999.
But cracks began to appear in his putting game early on Saturday. After making a nice chip shot from the bunker on the third hole, he missed a routine 5-footer for birdie-the first par-5 hole of the tournament he's failed to make birdie or better.
Oosthuizen then three-putted on the par-3 fifth hole for bogey-just his second bogey of the tournament-and let another birdie chance slip away on the sixth when his 25-foot putt stopped short of the hole by inches. He narrowly missed two more birdie putts within 10 feet on the eighth and ninth holes, settling for par on both.
While Oosthuizen was missing his putts, Els was sinking his: a 7-foot birdie putt on the fourth, a 3-foot shot for eagle on the par-5 seventh and another 3-footer for birdie on the ninth to pull within one stroke at the turn.
Els' solid round came undone, however, on the 580-yard, par-5 15th hole, which presents golfers with two paths to the hole: a safe route down the length of the curving fairway or a riskier, 250-yard jump over a reservoir straight to the green.
Els took the latter option and paid the price, plunging his second shot into the water. He managed to clear it with his next shot, but then missed an easy 5-footer on the green. He had been bogey-free up to that point in the tournament.