Rory McIlroy dropped three shots in his closing eight holes to card a scrappy opening round of 74 at the Valspar Championship in Florida.
The Northern Irishman started his round on the back nine and produced 10 straight pars at the PGA Tour event.
A double-bogey on his 14th hole of the day damaged his card, although he chipped in for birdie two holes later.
But a bogey on his final hole left him three over for his round, seven shots behind Canadian leader Corey Conners.
Scottish duo Russell Knox and Martin Laird are only two shots off the lead with holes still to play as round one continues, while Tiger Woods is at level par through six holes.
McIlroy, 28, arrived at the tournament stating he was “totally ready” for the Masters – the only major he is yet to win – which starts at Augusta National on 5 April.
The world number 12 began his 2018 season promisingly with a tie for third in Abu Dhabi and a runners-up spot in Dubai.
But he has followed those performances by missing the cut at the Pebble Beach Pro-Am, finishing tied for 20th at the Genesis Open and sharing 59th place at the Honda Classic.
In this latest outing at Innisbrook Resort and Golf Club, he drove the ball an average 308 yards but found the fairway just 46% of the time and hit greens in regulation with less than 40% of his approaches.