Rory McIlroy struggles to keep heat on Day and Lowry at Players Championship in Sawgrass
Rory McIlroy has plenty of work to do to get into contention at the Players Championship at Sawgrass after shooting a level par opening round of 72.
Australia's world number one Jason Day leads the way after a stunning nine under par 63, equalling the course record.
Irishman Shane Lowry is just two off the pace.
World number three McIlroy was among the later starters and stood level par with five holes remaining, the 27-year-old dropping a shot on the fourth and carding a birdie on the par-five 11th.
Fellow Ulsterman Graeme McDowell also shot a 72.
McIlroy will have to step it up today after a mixed round if he is to have any chance of landing his first victory of the year.
But Day, on this form, will take some catching.
Shane Lowry wrote his name into the record books with a stunning burst of scoring thanks to an "emergency" call to his coach.
The Offaly man was level par halfway through his opening round before storming home in a tournament-record 29 shots to card a seven-under-par 65.
The 29-year-old, who has recorded just one top-10 finish this season, holed from 35 feet for birdie on the 10th and chipped in for an eagle on the par-five 11th before picking up further shots from inside six feet on the 12th and 13th.
Lowry also birdied the par-five 16th and, after missing from 10 feet on the famous par-three 17th, made his final gain of the day from 12 feet on the 18th to finish two shots behind Day.
"Being honest, I was not very confident starting this week," said Lowry, who missed the cut in the Wells Fargo Championship last week.
"I had a bit of an emergency phone call with my coach this morning before I played. I just wanted to get some feelings off my chest. Things have not been going well and I did not feel comfortable on the golf course. I started okay and then obviously got going on the back nine and it's always nice to shoot 29 at some stage."
Lowry's 65 was matched by former US Open champion Justin Rose, Bill Haas, Cameron Tringale and Brendan Steele, with Italy's Francesco Molinari and Ernie Els among those on six under par.
Starting on the back nine, Day began his round with three straight birdies and also picked up a shot on the 17th before covering the front nine in 31 to match the course record shared by Martin Kaymer, Roberto Castro, Greg Norman and Fred Couples.
Playing partner Jordan Spieth, making his first appearance since squandering a five-shot lead with nine holes to play in the Masters, had to settle for a 72 after taking five to get down from a greenside bunker on the par-five ninth, his final hole.
Day, whose last competitive score at Sawgrass was an 81 in the second round 12 months ago, revealed he was disappointed to miss out on the outright record after narrowly missing from 40 feet on his penultimate hole.
"I just played solid tee to green and when I got to the green I was very confident with my putter," the 28-year-old said.
"Unfortunately it didn't go on eight, I really wanted to hole that putt to try and give myself a birdie on nine to beat the record but I'll take a tie.
"To be honest I just felt tired all day. I was just trying to grind it out as much as possible. It's been a long week because it's been hot the whole week. I just felt tired and that kind of distracted me from anything else."
Rose said: "It was great to come out and get off to another good start.
"I ordered a new putter a couple of weeks ago and it arrived this week, so it's nice to finally get it and it felt good. The pace felt much better and I'm happy."
Former champion Kaymer, Paul Casey and Russell Knox all shot 68, with Ian Poulter and Matt Fitzpatrick finishing three under and Masters champion Danny Willett a shot further back in his first tournament since Augusta.