Charl Schwartzel put himself in the driving seat heading into day two of the WGC - Dell Technologies Match Play after a comfortable win against Byeong-hun An at Austin Country Club.
The 2011 Masters Tournament champion only mustered one birdie on the front nine but his solid iron play and putting helped the South African ease to a 6 and 5 victory over the World Number 51, despite falling behind earlier in the match.
Schwartzel started the contest in positive fashion as he sank a 13-foot putt for par to go one up but An hit back at the second with a brilliant approach with his second shot let him two-putt for par to level the scores.
An went one up after the 185-yard fourth with a par when Schwartzel missed the green with his tee shot but the 11-time European Tour winner made it all square at the fifth when his approach to within five feet handed him his first birdie.
A par was enough for Schwartzel to go one up after the sixth despite finding the bunker as An missed a six-foot putt for a half before pars on holes eight and nine put him three up as the South Korean's putter continued to let him down.
Schwartzel sank a 15-foot putt to earn his second birdie of the match to go four up at the tenth before sinking successive birdies on the 12th and 13th to gain momentum for his second round robin match tomorrow.
In the other Group 12 clash, Paul Casey led one up over Joost Luiten through 13.
Luiten went one up at the second after his approach to 33-feet afforded him the chance to two-putt to take the hole before a birdie-par-birdie run from Paul Casey turned the match on its head to lead two up after 11.
Luiten responded with a birdie on the 12th before both players hit a par on the next in a see-saw battle.
In Group 5, debutant Hideto Tanihara was not showing any fear to go three up over two-time Major Championship winner Jordan Spieth after 13 holes.
After opening the first six holes with pars, Tanihara nailed the only birdie on the front nine from either player when he sank a 16-foot putt on the seventh which the American could not match.
At the turn, the Japanese player landed his approach to within two feet for a tap-in birdie with Speith failing to chip in for a half before Tanihara extended his lead with par on the 12th when the World Number Six found water with his second shot as a shock result looked to be on the cards.
In the other Group 5 match, Ryan Moore and Yuta Ikeda were all square through nine.
Thomas Pieters held a two up advantage over Scott Piercy after 11 holes in Group 13 when the Belgian took advantage at the third with a routine par after Piercy found the water.
The American hit back at the fourth with a birdie but Pieters responded at the next with a monster drive before chipping to 14 feet, which he sank to retake the lead before going further ahead with a par on the tenth after Piercy found the rough.
Bubba Watson was one up over Jhonattan Vegas after nine holes in the other Group 13 encounter.
In Group 4, Louis Oosthuizen led two up over Ross Fisher through nine with the South African gaining the incentive on the third after Fisher found water with his drive.
The Englishman responded with a wonderful approach to ten feet to level the scores with a birdie on the fifth but Oosthuizen hit back at the next with a birdie of his own when he reached the green of 590-yard par five in two to re-establish the lead.
Oosthuizen produced another great shot in to 12 feet on the eighth to seal his third consecutive gain to extend his advantage further.
In the other Group 4 clash, Hideki Matsuyama and Jim Furyk were all square after ten.
