Jason Day, Scott Piercy tied at the top at Firestone

Firestone continues to be a test for players, but Piercy managed a three-under 67 to join world number one Day (69) atop the leaderboard on Saturday.

The duo sit at five under, a shot clear of Swede David Lingmerth (69) in Akron, Ohio.

U.S. Open champion Dustin Johnson produced the best round of the day – a 66 – to be within three strokes of the lead.

Day held the overnight lead, but he could only hit three fairways throughout his round, yet still managed a 69.

"I hit some pretty errant shots out there today, but the short game saved me," the Australian told CBS Sports.

Day added: "There's obviously a lot of negatives that you can look at this round with regards to my hitting.

"The positive is that I'm still tied lead and I haven't hit the golf ball that great this week.

"If I can stick to that, and think about that, if I can hit it anywhere sort of decent tomorrow and give myself a few more opportunities on the greens I feel I've got a very good chance of winning."

Despite his struggles, Day had three birdies and two bogeys to remain in a share of the lead.

Piercy had an eagle at the par-five second, holing out from the bunker to make a great start to his round.

Only a bogey at the last cost him an even better round, but he is set to challenge Day.

Brian Stuard (67) is outright fourth at three under, a shot clear of Johnson, William McGirt (70) and Charl Schwartzel (67).

Jordan Spieth (71) is at even par and will need a huge finish to have any chance of challenging, while Adam Scott (73) slipped back to two over.