The world number one missed from 18 feet for birdie on the 10th and was unable to get up and down for birdie on the par-five 11th after a badly pulled approach.

Defending champion McIlroy and world number two Spieth had been paired together for the opening two rounds at Whistling Straits, along with Open champion Zach Johnson.

Rory McIlroy will play the first two rounds of the US PGA Championship with Jordan Spieth and Zach Johnson next week, if the world number one is fit enough to defend his title.