Alex Noren made five birdies on the front nine to take control of his Group 13 match against Thomas Pieters on day two of the WGC - Dell Technologies Match Play.
The 35 year old won his opener on Wednesday in convincing fashion and continued his fine form, going four up against the Belgian at the turn at Austin Country Club.
In the other Group 13 clash, Tony Finau was three up through eight against fellow American Kevin Na, with a winner-takes-all clash against Noren on Friday looking likely.
Jordan Spieth was two up after seven holes against Li Haotong in Group 4, while Charl Schwartzel and Patrick Reed were all square after five holes.
Noren won four of his last five holes on Wednesday in beating Na 4 and 2 and he was at it again straight away, hitting a stunning approach to seven feet to win the first.
A lovely tee-shot into the par three fourth left the Swede a 22-footer for birdie and he went two up before an approach to tap-in range on the par five sixth brought a fourth birdie of the day and three-hole lead.
A tee-shot to five feet on the par three seventh brought a fourth birdie in a row and Noren was already beginning to look out of sight.
Finau won his first three holes against Na with three pars and while his countryman eagled the sixth, he made a mess of the next to concede the hole.
Li fell behind on the first after bunker trouble but was back all square on the second when Spieth had to take a drop after a wayward second.
The Chinese must have thought he was going one up on the fourth when he holed a monster putt after Spieth had missed the green but the World Number Four holed his chip for a half.
Spieth has had some uncharacteristic putting woes of late but he made no mistake from six feet to edge ahead on the fifth, with a Li bogey on the seventh sending him two up.
Schwartzel's approach to five feet at the second had brought him a birdie to go one up but Reed holed a 20-footer on the fourth to level things up.
