Hideki Matsuyama surged into a share of the lead on day four of the WGC-Bridgestone Invitational but Rory McIlroy was also on the move at Firestone Country Club.
The World Number Three already has a World Golf Championships title to his name at the WGC-HSBC Champions and he picked up three shots in his first four holes to get to ten under alongside Thomas Pieters.
The big-hitting Belgian picked up a single stroke in his first three holes, while McIlroy was three under after six to sit just a shot back.
Zach Johnson was also at nine under, a shot clear of Scott Hend, Charley Hoffman and Paul Casey.
Russell Knox was then seven under with Adam Hadwin a further shot back.
Knox has made hay on the the opening holes all week and when he put his approach on the first to six feet and took advantage of the par five next, he was nine under for those two holes and seven under for the tournament.
Playing partner McIlroy, and Hadwin and Hoffman in the group behind, also capitalised on the second and they too were two shots behind the leaders who were about to tee off.
Both Pieters and Johnson parred the opening hole but were soon joined by Matsuyama who spectacularly chipped in from 58 feet from the back of the second green for an eagle.
Ahead at the fourth, McIlroy holed a 37-foot double-breaker to get within a shot of top spot, while Casey birdied the second, third and fourth to join the group at seven under.
The final pairing became the latest players to birdie the second but Matsuyama also got to double figures when he holed from three feet on the third.
Casey was on the charge and he made a fourth birdie of the day on the sixth, with Hoffman making a gain on the fourth to join him at eight under.
Johnson bogeyed the third to drop to nine under where he was soon joined by McIlroy, holing a 29-footer on the sixth.
Hend began his day with four pars.