Ireland's Padraig Harrington spectacularly rolled in three successive putts from more than 20 feet to grab a two-shot lead in Thursday's opening round at the WGC-Bridgestone Invitational. Competing in his first tournament since the British Open three weeks ago, the three-time major winner fired a flawless six-under-par 64 at Firestone Country Club. Having teed off at the 10th, Harrington did well to save par at the sixth by rolling in a 21-footer before adding birdie putts from 26 and 23 feet at the seventh and eighth. He then parred the ninth to end the day two ahead of Thailand's Prayad Marksaeng, American Scott Verplank and South African Tim Clark in the elite World Golf Championships (WGC) event. Americans Steve Stricker and Zach Johnson and Britain's Ian Poulter opened with matching 67s while world number one Tiger Woods, bidding for a record seventh title at Firestone, carded a 68. Prayad, a six-time winner on the Asian Tour, was delighted with his display after teeing off in the second group of the day on the par-four 10th hole. “Conditions were very nice and I was really happy with my start,” the 43-year-old told reporters, speaking through an interpreter. “The greens were quite fast but I like them fast. “When I came here last year, I felt really comfortable with the course. It's very similar to the Japanese golf courses that I played on the Japan Tour.” Clark, who tied for sixth at Firestone two years ago after previously struggling on the tree-lined layout, said he had benefited from adopting a more positive attitude at the venue. “I used to get quite frustrated around here because I felt like I'd hit a lot of good tee shots and the ball would just kick off into the rough,” the three-time European Tour winner said. “The rough used to be a lot thicker here and that made it really tough for a guy like me,” added Clark, one of the shorter hitters on the circuit.