Rory McIlroy knew his ailing ankle wouldn’t let him down, but the world No.1 wasn’t so sure about his game as he stood on the first tee of the PGA Championship on Thursday.

“I was pretty nervous on the first tee,” McIlroy said of contemplating his first ball struck in anger since the US Open in June.

“It was nice to get that opening tee shot out of the way.”

McIlroy’s return from a torn ligament couldn’t have come in a brighter spotlight.

The defending PGA Champion was paired in a super-group with Masters and US Open champion Jordan Spieth and British Open winner Zach Johnson as the final major of 2015 got underway at Whistling Straits.

Playing in tough afternoon winds, none of the trio could match the six-under par 66 posted by first-round leader Dustin Johnson in the morning.

McIlroy and Spieth both carded one-under 71, while Zach Johnson settled for a three-over 75.

McIlroy opened with a bogey, but promptly bounced back with a birdie at the second.

“It wasn’t the best of starts, but to hit those two shots on the second hole and make birdie, that sort of settled me down and I could get into the round,” the 26-year-old said.

Another bogey-birdie combination at eight and nine saw McIlroy even at the turn – not before an impressive par save at the par-five fifth from the shallow water of a pond.

McIlroy was in a bunker off the tee of the 603-yard fifth. He pitched out into the fairway and his third shot trickled into the water hazard.

McIlroy rolled up a trouser leg and waded in, splashing the ball to some six feet and making the par putt.

“The only thing I was trying not to do was get my feet wet,” McIlroy said. “I just had to remember to hit it hard, and I was very fortunate to escape with a par there.”

McIlroy who added birdies at 11 and 16 before closing with a bogey, said his ankle felt fine – just as it had when he played practice rounds in Portugal last week.

“The only thing I was a little bit worried about, going into today is whether I could bring this good golf that I know that I have been playing into a competitive round,” he said.

He’ll need to keep the good golf up, to have a chance of catching Dustin Johnson and fend off Spieth’s bid for the world No.1 ranking.