Pieters leads by one over Scotland’s Russell Knox with the group of six at 3 under par 67 including Jordan Spieth, Bubba Watson, Rory McIlroy, Jon Rahm, Ross Fisher and Kevin Kisner.
Pieters was mistake free in that he did not drop any shots in his round of 65, a lengthy putt for birdie at his last hole (the 9th) edging him clear.
The Australian contingent is headed by previous winner of this event, Adam Scott, who, in fact, got to the lead at 5 under through 11 holes before a series of bogeys would see him finish with a round of 1 under 69 to be tied in 9th position.
Soft bogeys at his final two holes was a disappointing way to finish for Scott who won here in 2011 and has several other top tens to his name around the Firestone Country Club.
Of the other Australians Scott Hend recovered from a slow start to finish with a round of even par and a share of 22nd position, Jason Day is 33rd at 1 over 71, Rod Pampling and Marc Leishman recorded rounds of 73 and Sam Brazel 74 after being well placed with just a few holes to go.
JASON DAY - THE LOVE OF GOLF