Graeme McDowell enjoyed a welcome return to form as he carded an opening 66 to take a share of second place on day one of the WGC-Bridgestone Invitational.
New Zealand's Danny Lee shot a five under par 65 to claim the overnight lead in Ohio, with McDowell and America's Jim Furyk one stroke further back.
McDowell has managed just one top ten finish this year, a share of ninth place in the Omega Dubai Desert Classic in February, but the former US Open Champion impressed on Thursday, carding four birdies in a front nine of 31 before making another gain at the tenth.
After dropping his first shot of the day on the 12th, the Northern Irishman found par on the next six holes to go into the clubhouse four under par.
The Ryder Cup player, who has now shot 66 in each of his last three rounds at Firestone Country Club, said: "I have just been working hard the last ten days or so on some of the things I have not been doing well; principally driving the ball and putting the ball, which are two things that I have always been pretty strong at that have been eluding me lately.
"I drove it well today, especially on the front nine. I struggled a little bit on the back nine.
I felt like the game got a good workout today, some good shots and some good hanging in and some good putts.
"It was a good workout, a nice score, and I look forward to getting back at it tomorrow."
Lee, starting at the tenth tee, opened his round with back to back birdies before dropping a shot at the par three 12th.
A further gain at the 13th was followed by a second bogey two holes later but he bounced back immediately with another birdie at the 16th to reach the turn in 33.
Three birdies in four holes on the front nine put Lee in the driving seat and he closed out his round with five pars to take the outright lead.
Lee said: "It was a good day for me.
"I left a couple of short birdie putts out there. It may sound a little bit too greedy, but I did.
"I was hitting it that well, and I was very happy with my result."
Furyk looked set to join Lee at the top of the leaderboard before a bogey at the par four 18th saw him slip to four under.
Meanwhile England's Justin Rose carded four birdies in the first six holes before a bogey at the eighth took him to 32 at the turn.
Nine straight pars on the back nine saw Rose finish two shots off the lead on three under par, alongside World Number Five Rickie Fowler.
Rose said: "My round was pretty much all in the first six holes today.
"I got out of the gate incredibly quickly. Before my round, I realised the course was not yielding low scores today, and I almost surprised myself to get off to such a quick start.
"I am very happy with my start. Obviously three under on this course sets you up nicely for the week. Yeah, a perfect start."
Sweden's Henrik Stenson, Englishmen Lee Westwood, Ian Poulter and Paul Casey, and France's Victor Dubuisson are among a large group on two under par.
