If he was frustrated by that it did not show as he nearly holed his pitch for eagle at the 601-yard sixth, allowing him to finally get into red figures.
McIlroy, who won the British Open in 2014 and missed the defense of the claret jug previous year because of injury, shot a 2-under 69 and was three strokes off early leader Patrick Reed. To do that, he needs to win and have current No. 1 Jason Day finish outside the top 10.
This week's Open championship will mark the start of an exciting run of big tournaments for Lahiri which includes the PGA Championship in a fortnight and the Olympic Games in Rio de Janeiro where he has qualified with S.S.P. Chawrasia.
Reed and Open debutant Thomas also clocked the same score over 12 and 13 holes respectively.
Elsewhere this afternoon, Padraig Harrington had a mixed day on the course but finished strong to leave him on one under par.
Bowditch, who briefly led on moving day past year, is well on the way to missing the halfway cut for the eighth time in a dozen starts after racking up a nine on the brutal par-4 11th.
But they were the last birdies Leishman made all day as he ground out four straight pars, including a fantastic up and down at the Postage Stamp par-3 8th hole when he found the deep greenside bunker with his shot from the tee. Oosthuizen also made an ace at the Masters earlier this year, which means he now has more holes-in-one on the back nine of major championship courses this year than most of us will ever have in our lives.
The five-time major victor got off to a blazing start at the Open Championship, tackling Royal Troon in Scotland with a dominating first-round performance. It was a proud moment for the 53-year-old Scotsman but things quickly turned sour.
"Nobody in the field would have got that first ball out, it was buried right in the face of the bunker". An up-and-down later, Monty was walking off with a double-bogey 6 from one of the easiest holes at Troon. "Obviously I'm playing very well right now".
Colin Montgomerie has started what could be his final British Open with an even-par 71 at Royal Troon.
"It was theatre really - until I hit my second shot!" But Matt Jones, Rory McIlroy and Bubba Watson, among others advanced to four or even five under and then retreated. He couldn't keep it going, settling for three bogeys on the tougher inward nine to fall off the leaderboard.
"It was a great honour for me and for the family and the members of Troon that I kicked this off this morning".