Rory McIlroy made a nervy start on his return from injury as he bogeyed the first hole at the US PGA Championship on Thursday.

The world number one was unable to defend his Open title at St Andrews last month after damaging ankle ligaments while playing football with his friends. 

McIlroy declared himself fit for the final major of the year at Whistling Straits, but was immediately on the back foot by missing a relatively short putt to start with a five.

All eyes were on McIlroy, Jordan Spieth and Zach Johnson when the stand-out group of the day teed off at 1.20pm local time in Winconsin.

Spieth, who is aiming to replace McIlroy at the top of the rankings, and Open champion Johnson made a solid start with pars at the first. 

Dustin Johnson carded a six-under 66 to take an early lead as he attempts to end his wait to win a first major.