Rory McIlroy conquered his nerves and tougher afternoon conditions to lead the Irish charge on his injury comeback in the US PGA at Whistling Straits.

The world No 1 fired a one under 71 in his first competitive round for 53 days after missing five weeks with ruptured ankle ligaments.

And despite a bogey at the last the Holywood star was just five shots behind leader Dustin Johnson, who fired super 66 to lead by one from Swede David Lingmerth on six under.

Admitting he was nervous before the start, the Ulster ace began with a disconcerting three-putt bogey at the first. But he birdied the par-five second to get back to level par and followed a bogey at the eighth with birdies at the ninth, 11th and 16th before handing back a shot at the last.

Pleased to be back and match playing partner Jordan Spieth and happy to save some crucial pars despite a 32-putt round, McIlroy said: “I was trying to hold on the front nine and there were a few more chances on the back with the par fives.

“It’s great to be back obviously but I was quite nervous on the first tee not having hit a competitive shot in nearly two months. 

“I was always going to be a little bit nervous and while it wasn’t the best of starts, the two shots on the second hole settled me down and I was off and running from there.

“The ankle feels great. It has felt great all week. I can go after it and I have full confidence in it.”

McIlroy's par save at the par-five fifth, where he was at the water's edge in three but splashed out to 12 feet with his trouser legs rolled up, had his fans gushing.

"It was fine," he said. "The only thing I was trying not to do was get my feet wet. Because if the water gets through this shoe and through, then the tape gets wet and then that would be a little more than just sort of annoying or uncomfortable for the rest of the day.

"But it was fine. I just, it was a little bit deeper on the right side, so I just rolled my right trouser leg up and it was fine. I just had to remember to hit it hard. And I was very fortunate to escape with a par there."

He added: “I was just a little bit anxious coming back and seeing how my game’s going to react whenever I’m put under a little bit of pressure and have a card in my hand and have to really score. 

“And once I got those first couple holes out of the way, I felt like I settled into the round really nicely. I’m a little disappointed with my finish, but overall it was a pretty good round.

“The ankle felt great, like it has done all week. It’s not an issue at all and anyone can see that with the way I was hitting it out there.”

While Johnson shot his 66 in the calmer morning conditions when the greens were a little softer, McIlroy and the rest of the Irish did battle with stronger westerly winds and a firmer course in the afternoon 

“We are due a bit of wind again on Sunday, so maybe the conditions will be a little more scoreable tomorrow and Saturday," McIlroy said. "There are holes you have to take advantage of on this golf course, like the par fives, and you hang on elsewhere. 

“There is a lot of trouble out there and a couple of times I had to take my medicine. As long as you make more birdies than bogeys you will be alright. I didn’t hit that bad a tee shot on the eighth hole but got caught in a bad lie. So things like that.

“It was one of those days where sometimes it was good to make a par and move on. I realised that and there were a few holes on the back nine I could take advantage of. Thankfully I took a couple of them on the par fives. 

“I’m in the tournament. It was very important for me not to go out there and shoot myself out of it right away. So to be there only five off the lead, playing in the tougher conditions – I wish I could have been one or two shots better – but hopefully I will go out there on the back nine tomorrow where there are some chances, and get off to a good start.

“The ankle is a non-issue. I’m stretching it because I want to keep it mobile and more out of habit than anything else after the last few weeks. I think you can see with the swings I’m making that I’m confident in it.”

McIlroy was tied for 24th at the finish but WGC-Bridgestone Invitational winner Shane Lowry crashed back to earth with a 78 leaving alongside Ryder Cup skipper Darren Clarke.

Graeme McDowell finished with three bogeys at the 16th, 17th and 18th for a one over 73 as Padraig Harrington bogeyed the last for a four over 76. 

After three putts from long range at the 16th from range, McDowell failed to get up and down from sand at the 17th and then three putted the 18th.

And he was frustrated to let his score slip away with 30 putts and two late three-putts after a brilliant ball-striking round in which he his 11 of 14 fairways and 11 of the last 14 greens in regulation.

Determined to battle back to the top after a tough start to the year, G-Mac said: “I played beautiful all day. Putting was difficult today - a lot of the greens are quite exposed and I left a lot of putts out there today. 

“I missed the ninth fairway and missed a short one for par there and hit a bad tee shot on 16 and got out of position and three putted from long range for bogey there and the last two holes were very disappointing.

“It was just a round of what could have been. I played the golf, I just didn’t hole the putts. I putted pretty awful to be honest.”

McDowell’s driving and putting are the strengths of his game but having struggling that department over the past six months, he has slipped from 15th to 61st in the world.

Still, there have been good signs in recent weeks and his first round, while disappointing as a scores, bodes well in many ways.

“It’s small steps,” McDowell said. “I can’t expect it all and it’s not giving me it all. But that’s fine. I am really, really happy with the way I have hit the golf ball today. 

“Tee to green I could not play much better than I did today. You finish with three bogeys on the bounce there and it just leaves a sour taste. But it was an afternoon that could have gotten away and it didn’t and we will go again tomorrow morning.

“I just need ball striking rounds like that where I hole a few more putts. It is confidence levels and belief levels and that’s just a frustrating round because I did everything I asked of myself except get the ball in the hole. 

“I know I am a good putter. I just have to get a little more comfortable and want it a little bit less and let it come.”

Asked the root of his problems recently, he said: “It’s been my driving and my putting. They are the two things that have been my stalwart go-tos.

“I drove it well today and made two mistakes and they cost me bogeys in the end. That’s this course in a nutshell. 

“A lot of the high tariff tee shots I played well and I hit some great iron shots and hung in there well at times and just couldn’t seem to.. tee to green only a dozen guys hit it better than me today.

“I really felt like I did all the right things tee to green. That’s golf though.”

Lowry played just 18 holes in practice and he was always going to find it tough to follow up his breakthrough WGC-Bridgestone Invitational win last Sunday with another big performance.

After lipping out for birdie at the first, he got a flyer and bogeyed the second, double bogeyed the third after a poor tee shot led to a miscued recovery that almost went into Lake Michigan and then dropped shots sixth and ninth to turn in five over 41.

He birdied the 10th and 11th to get back to three over but then dropped three shots in a row from the 12th and did well to hang on with four closing pars.

“I struggled with the pace of the greens but I am not going to stand here and claim being tired or anything like that,” Lowry said, visible less annoyed that he might usually be after a 78.

“While I did feel a little tired, it was no excuse as I made some poor decisions out there.

“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.”

Harrington was under pressure from the moment he double bogeyed the fourth and then dropped shot at the sixth and ninth to turn in four over 40.

Five over after a bogey six at the 11th, he birdied the short 12th from three feet and the 14th by burying a 40 footer.

But while he blamed his chipping - he scrambled for par five times out of 10 —  he also hit just three of 14 fairways and it was a poor drive which left him needing to get up and down from 158 yards at the 18th to avoid a bogey.

In the end, he had to chip and putt to save a bogey and while he dismissed his bad right knee for his score, he admitted it made it tough to walk a difficult course.

“I missed half a dozen chip and putts out there and on a tough day you can’t afford to do that,” Harrington said. “That’s why I shot 76.

“My knee is just an issue I am dealing with. It didn’t affect my golfing anyway, that’s for sure. It affected me walking around the place, but not anything else.”

Lily to need a 69 to make the cut, he was asked if he was fit enough to get through Friday, he said: “Yes, absolutely. No doubt about it. Hopefully in the morning it will be better.”