Former winners Ross Fisher and Padraig Harrington experienced contrasting starts when the Dubai Duty Free Irish Open got under way at the K Club on Thursday.
As heavy rain showers greeted the early starters, 2010 champion Fisher birdied three of his first five holes to move to the top of the leaderboard, a shot ahead of Wales's Bradley Dredge and England's Andrew Johnston.
Uh Oh... Padraig Harrington opened with a birdie but followed with a 7 on the par four, 11th hole at the #IrishOpen He's now 2 over after 2— Des Cahill (@sportsdes) May 19, 2016
But after starting his round on the back nine with a birdie on the 10th, three-time major winner Harrington ran up a seven on the 11th to slump to two over par.
Harrington, who defeated Dredge in a play-off at Adare Manor in 2007, found a fairway bunker off the tee and pushed his recovery shot into the trees, from where he could only hack out sideways.
The 44-year-old's approach then came up short of the green and after chipping to two feet, he missed the putt and tapped in for a triple bogey.
On the other side of the course, Dredge had started with six straight pars before carding birdies on the seventh and eighth, while Spanish Open winner Johnston had opened with birdies on the 10th and 11th.
Tournament host Rory McIlroy was among the later starters as he looked to end a streak of three straight missed cuts in his home event, the world number three also seeking a first win of the season after six top-10 finishes.
Players and caddies were wearing black ribbons as a mark of respect to former Ryder Cup star Christy O'Connor Snr, who died last week at the age of 91.
It was Fisher's turn to card a seven when he found trouble on the par-five 16th, but the former Ryder Cup player bounced back to birdie the 18th and reach the turn in two under par.
In the tough conditions that was good enough for a share of the lead with Dredge, Tyrrell Hatton and France's Thomas Linard, with Harrington five shots off the pace after following a double bogey on the 15th with a birdie on the 16th.
Former Ryder Cup captain Paul McGinley was level par after nine holes, with Shane Lowry - who won the title in 2009 while still an amateur - a shot further back after eight holes.