Rory McIlroy opened up a one hole lead against Zach Johnson midway through their round of 16 tie at the WGC-Dell Match Play.
Johnson has been the outstanding player so far this week at Austin Country Club, needing just 42 holes to win his three group matches, while McIlroy has taken 55, including 20 against Kevin Na on Friday.
But the defending champion has won his last ten matches at this event and a birdie on the eighth was enough to get his nose in front at the turn.
McIlroy got off to a poor start, with a chip shot advancing less than two feet as he conceded the first, but Johnson missed from inside five feet to drop the second and a brilliant McIlroy approach saw him win the next.
Another poor chip from the Northern Irishman allowed Johnson to take the fourth before the next three holes were shared but when the American found a bunker with his second shot on the eighth, a par was enough to move McIlroy ahead.
The winner of that match will face Bill Haas or Chris Kirk, with Kirk two up at the turn in their clash.
Brooks Koepka held a two hole lead over 2013 champion Matt Kuchar after eight holes of their last 16 contest, with World Number Two Jason Day one up through seven holes against Brandt Snedeker.
