JB Holmes remains in control at the WGC-Cadillac Championship despite a one-over 73 in his second round on Friday.
The American produced a stunning 62 to open the tournament at Trump National Doral, but failed to get anywhere near the same levels again.
A double-bogey at the par-four 18th was particularly costly as he finished the day at nine under overall.
Ryan Moore (71) sits two shots back at seven under, while Adam Scott (68) is at six under at his first event of the year.
Bubba Watson (69) and Henrik Stenson (71) are tied for fourth a further two shots back.
Rory McIlroy endured another tough round, his 70 lifting him into one under for the tournament and into a tie for 11th.
But the Northern Irish world number one did have a regretful moment at the eighth, throwing his three-iron into the water having also sent his ball there.
Holmes lit up the course in Miami on Thursday, but the overnight leader started slowly with two bogeys and a birdie in his first three holes.
The 32-year-old mixed another birdie and bogey before the turn and he looked back on track when he birdied the 10th hole.
After a bogey at the 13th, Holmes birdied holes 16 and 17 before the costly double-bogey at the last.
Moore's round was far more consistent as he mixed two birdies with a bogey, while Scott - using a short putter - made six birdies in his round.
Americans Dustin Johnson (73) and Ryan Palmer (70) are tied for sixth alongside Frenchman Alexander Levy (73).
Welshman Jamie Donaldson (72) and Spaniard Sergio Garcia (69) sit at two under, tied for ninth.