Tiger Woods' driver made its first appearance of the week, but it was two shots from the longest club in Lee Westwood's bag which helped ignite The 142nd Open Championship.
Woods had employed a conservative strategy over the first two days at a parched Muirfield and it looked to be paying dividends when he briefly moved into the outright lead early in the third round.
But the World Number One was outshone on the fifth hole as playing partner Westwood made a brilliant eagle to vault to the top of a crowded leaderboard.
Both players had split the fairway on the 559 yard par five, Woods by using a driver for the first time, with Westwood then hitting his driver again and getting a good bounce to leave his ball just short of the green.
The 40 year old, putting superbly since working with 1991 Open Champion Ian Baker-Finch, was faced with a testing putt from around 35 feet but promptly holed it for a three to move to three under par.
Woods' second shot with a fairway wood had come up short left of the green and, after pitching to seven feet, the 14-time Major winner missed his birdie attempt to remain two under.
Overnight leader Miguel Angel Jiménez, seeking to become the oldest Major Champion at the age of 49, was also two under after a dropped shot at the second.
Former Masters Tournament champions Zach Johnson and Angel Cabrera were a shot behind alongside four-time Major winner Phil Mickelson and Sweden's Henrik Stenson, while Sergio Garcia and Brandt Snedeker led in the clubhouse on three over after rounds of 68 and 69 respectively.
Scotland's Martin Laird had seen his hopes of a famous home victory lengthen when he ran up a nine on the par four third after taking two penalty drops from the heavy rough.
Westwood saved par superbly from a greenside bunker on the sixth and an excellent tee shot on the next set up a birdie from five feet.
And with Woods dropping a shot there after a poor chip from over the green, Westwood suddenly had a three shot lead on four under, with only four players under par.
Almost as soon as Westwood's big lead was created it was gone, the former World Number One three-putting the eighth for a bogey and dropping another shot on the ninth after finding sand off the tee and hitting a poor chip from the back of the green.
Woods got up and down from a greenside bunker for a birdie there to join Westwood at the top of the leaderboard on two under, with Spain's Rafael Cabrera-Bello and American Hunter Mahan a shot behind, Mahan with just one to play.
Westwood reclaimed the outright lead at three under with a birdie from close range on the 14th, where Woods had to save par from a greenside bunker.
Jiménez got back into red figures with a birdie on the 13th, but Cabrera's challenge stuttered as he fluffed a pitch on the 16th to run up a double bogey five and fall back to one over.