Jim Furyk managed to hold on to the lead on day three of the WGC-Bridgestone Invitational, but Louis Oosthuizen is just one shot behind.
Furyk was five strokes clear at one stage during his round but it was cut to just one at the finish after only managing to go round the Akron course in level par to remain on 11 under overall.
Oosthuizen moved into second place with three birdies in his last 10 holes after he had bogeyed the par-four eighth, while Keegan Bradley was a further three shots back in third.
American Furyk, who followed up a magnificent opening round of 63 with a four-under 66 at the Firestone CC (South Course) yesterday to open up a two-stroke lead, was rather more subdued today.
He picked up just the one birdie at the par-five second to move to 12 under but fell back after dropping a shot at the par-three 13th.
His closest challenger overnight had been Rafael Cabrera Bello but the Spaniard saw his chances of victory evaporate after an horrendous seven-over-par 77 that drops him back to two under.
It was therefore left to 2010 Open champion Oosthuizen, who has dropped just three shots in Ohio this week, to close the gap on Furyk.
Bradley has a chance of catching the frontrunners after his three-under-par 67.
Northern Ireland's Rory McIlroy was a shot further back in a tie for fourth overall alongside Steve Stricker of the United States. Graeme McDowell shot a level par round of 70 to remain on -3 and a share of 11th place.