MEDINAH, Ill. -- Justin Thomas tied the course record with an 11-under-par 61 to surge to a commanding lead of the BMW Championship in the third round Saturday, Aug. 17, at Medinah Country Club in Medinah, Ill.

Thomas moved to 21-under 195 through 54 holes, good for a six-shot lead going into Sunday's final round.

Tony Finau (who shot 68) and Patrick Cantlay (68) are tied for second place, followed by South Africa's Rory Sabbatini (67), who holds fourth alone at 14 under.

Thomas, 26, began the round with birdies on the first five holes. His lone blemish came with a bogey on the par-4 sixth, but he bounced back with a birdie at No. 8.

Thomas scorched the backside in 6 under, aided by a pair of eagles. At the par-5 10th, he hit a 259-yard approach to just three feet for a tap-in, then holed his 180-yard approach on the par-4 16th. He also used a chip-in for a birdie at the par-5 14th and rolled in a 6-footer for birdie at the par-3 17th.

Thomas entered the tournament -- the second of three tournaments in the FedEx Cup Playoffs -- in 15th place in the FedExCup standings.

If Thomas wins the BMW Championship, he'll move atop the standings.

Finau had an eagle on the fourth hole -- holing out from 119 yards on the par-4 -- and was 4 under for the round until a bogey at No. 9. He played the backside at 1 under.

Cantlay had his only bogey of the round on the 16th hole. He closed with a birdie on the final hole.

Spain's Jon Rahm (66) is alone in fifth place at 13 under. He had the fourth-best round of any golfer in the field, but the gap grew between him and Thomas.

Brandt Snedeker (67), Lucas Glover (69) and Canada's Corey Conners (69) share sixth place at 12 under.

Second-round leader Hideki Matsuyama of Japan shot 73, falling to a ninth-place tie at 11 under alongside Rickie Fowler, Kevin Kisner and Xander Schauffele.