No dodgy ankle. No rust. Nothing. Just the same old Rory McIlroy, striding down the fairways with a pep in his step.

And the world number one stood toe-to-toe and stared eyeball-to-eyeball with his would-be usurper Jordan Spieth in a first round of the US PGA Championship here at Whistling Straits that had both players opening their quests for the season's final Major title with a pair of 71s, one-under-par.

A bogey on the Par 4 18th hole - which played as the toughest of all averaging 4.65 - was the lone blot on McIlroy's back nine, which left him five strokes behind first round leader Dustin Johnson.

“I felt it was good. It was a good solid round of golf, I’m happy with the way I struck the ball,” confessed McIlroy.

Playing in the toughest of the conditions, with a strong wind whipping in off Lake Michigan, the 26-year-old Northern Irishman - who was returning to tournament play for the first time since rupturing his ATFL ankle ligament on July 4th which forced him to miss out on defending both the British Open and the WGC-Bridgestone Invitational - showed no signs of discomfort despite the undulating terrain.

At one stage of his round, after an errant approach to the fifth, McIlroy was forced to roll up his trousers and plonk his Nike shoes into the lake to play a recovery shot. He managed to get up and down from the water to save his par there, and there were other occasions he had to play from wild lies. Each time, he demonstrated there was no lingering ill effect from the ankle injury. “I have full confidence in it, it doesn’t bother me one bit,” he said.

After turning in level par, McIlroy added birdies on the 11th and 16th before that late, finishing bogey. But there was no despondency afterwards, the opposite if anything: he had shown his fitness and signalled his intent.

“I was a little anxious coming back (playing) and seeing how my game’s going to react whenever I am put under a little bit of pressure and have a card in my hand and have to really score. Once I got those first couple of holes out of the way, I felt I settled into the round really nicely,” added McIlroy.

For the other Irish players in the field, it was a hugely disappointing start to the championship. For a long time, Graeme McDowell stuck stubbornly to his task and approached the finishing stretch in fine fettle. But a bogey-bogey-bogey finish left a sour taste, as McDowell signed for a 73.

“It was just a round of what could have been, because I played the golf, I just didn’t hole the putts. I putted pretty awful, to be honest. It was a frustrating round, disappointing round, because I did everything that I asked of myself today except get the ball in the hole. So I know I’m a good putter, I just have to get a little more comfortable and just let it come,” said McDowell.

There was disappointment too for Shane Lowry, who had hoped to bring the momentum from his great WGC-Bridgestone Invitational success with him to Wisconsin. It didn't happen. The Offalyman signed for a 78, six-over, that puts him in a real battle if he is to survive the cut. "My head seemed to be all over the place and I definitely wasn't the calm fella who won at Firestone last Sunday, so it was just one of those days that things didn't go for me and I need to get out there tomorrow and try and shoot a good score and see what happens after that," said Lowry.

Lowry added: “There I also struggled with the pace of the greens but I am not going to stand here and claim being tired or anything like that, and while I did feel a little tired, it was no excuse as I made some poor decisions out there.”

Pádraig Harrington bogeyed the 18th to sign for a 76, having battled back from a tough opening nine with a pair of birdies on the homeward run. Darren Clarke, like Lowry, signed for a 78.