Rory McIlroy faced an uphill battle to claim a second WGC-Bridgestone Invitational title as the £7.5million event headed for an exciting climax in Akron.
McIlroy began the day three shots off the lead shared by Ryder Cup partner Thomas Pieters and Zach Johnson, but made the ideal start with three birdies in the first six holes at Firestone Country Club.
However, after finding rough off the ninth tee and coming up short of the green, the four-time major winner hit a clumsy pitch which ran through the green and failed to get up and down to save par.
That dropped McIlroy back to eight under par and three shots behind world number three Hideki Matsuyama, who had chipped in for an eagle on the par-five second and also birdied the third and sixth.
At 11 under par, Matsuyama was a shot ahead of Pieters and American Charley Hoffman, with Hoffman carding four birdies in the first seven holes and Pieters picking up a shot on the par-five second.
Johnson was a shot further back after following a birdie on the second with a bogey on the third, with Scotland’s Russell Knox alongside McIlroy on eight under thanks to birdies on the first, second and eighth.
McIlroy’s victory at Firestone in 2014 was sandwiched between major titles in the Open Championship and US PGA, but the 28-year-old has failed to win a major since and split from his long-term caddie JP Fitzgerald after finishing fourth at Royal Birkdale last month.
The Northern Irishman has employed his best man Harry Diamond - a former top amateur in his own right - in Akron and for next week’s US PGA at Quail Hollow, where he won his first PGA Tour title in 2010 and set the course record of 61 on his way to a seven-shot victory in 2015.
Open champion Jordan Spieth needs to win the US PGA to complete a career grand slam, while McIlroy requires a victory in the Masters to join Gene Sarazen, Ben Hogan, Gary Player, Jack Nicklaus and Tiger Woods in having won all four of the game’s biggest events.