Ernie Els was holding off the challenge of compatriot Charl Schwartzel and Ireland's Padraig Harrington as the World Golf Championships-CA Championship entered its last nine holes in Miami.
Without a win for two years, Els birdied three of the first four holes and opened up a three stroke gap.
But his fellow South African, at 25 the younger by 15 years and with two European Tour titles to his name already this season, birdied the sixth and seventh to be only one behind.
He then levelled things up with a 12 footer on the next, but Els was on in two and two-putted to reach 16 under par.
Harrington, meanwhile, was four shots back in third after managing only one birdie on the outward half.
It came at the 394 yard fifth thanks to an 82 yard pitch to three feet.
The rest of the chasing pack looked as if they might have too much ground to make up.
German Martin Kaymer was 11 under starting for home, while Northern Ireland's Graeme McDowell climbed all the way to joint fifth on ten under with five successive birdies around the turn.
Paul Casey started the day with hopes of climbing into the hunt. He had to wait until the long eighth for his first deviation for par, but when it came it was a 15 foot eagle putt and by converting a 33 footer for birdie at the tenth he joined McDowell.
Schwartzel got back on terms yet again at the tenth, but went over the green into sand on the next and failed to get up and down.
The ding-dong battle continued at the long 12th, Schwartzel making an eight footer to go joint top on 16 under, but Els holing from four to edge ahead once more.
Harrington had birdied the long tenth despite having to play his third shot with his feet on the rocks by the lake, but a bogey at the short 13th left him five adrift.
McDowell completed a six under 66 to be in a tie for fifth on ten under.
He said: "I never thought for one second I could get into the hunt, but this is a great boost for me."
Schwartzel had hopes of drawing level for the eighth time over the weekend when Els twice found rough on the 14th, but the former Open Championship winner made a 24 foot par putt to stay in the outright lead.
It was almost certainly a two-man race by then with Harrington having three bogeys in a row from the 13th to drop to joint fifth.
Schwartzel was five clear of third-placed pair Martin Kaymer and Matt Kuchar.