Rory McIlroy believes he can still retain the Arnold Palmer Invitational despite slipping seven strokes behind Keegan Bradley and Tommy Fleetwood at a punishing Bay Hill.

As Graeme McDowell fell back to 43rd on one-under after a 75 and Shane Lowry crashed out after a 79, McIlroy mixed the extraordinary with the ordinary in adding a 70 to his opening 72 to share 31st on two-under.

"The golf course is hard,” McIlroy told the Guardian. “It’s playing trickier than it did last year. It’s just about staying patient. If I hit fairways over the next two rounds than I still feel like I have a good chance.”

The defending champion got off to a sluggish start in Orlando, sandwiching a birdie at the 13th (his fourth) between bogeys at the 11th and 18th.

He quickly sparked to life on his homeward nine and reeled off birdies at the first, third and fourth before following a bogey at the fifth with an otherworldly eagle three at the sixth.

The world number six man reduced the 532-yard par-five to a drive, a six-iron and eight-foot putt and while another birdie would have moved him into the top ten, he bogeyed the eighth to leave himself playing catch up.

Fleetwood eagled the par-five sixth and 12th in a six-under 66 before being joined on nine-under by Bradley, who fired a 68.

Then American then aimed another jibe at golf's rule-makers after his round following recent decisions made under the revised rules.

"I think that it would be nice if we never heard from the USGA,” Bradley said. “The more you hear about it, the more issues probably are happening, whether people are getting penalties or -- it would be nice if we never heard or got asked questions about the USGA because they should be off to the side and hopefully the rules are here to help us and help us play.

“I don't know what to think of the USGA anymore. They're kind of doing their own thing. But we're trying our best to figure them out and I just, it's a shame when you see it affect other players on the course and affect their livelihood, and I hope that we did get all that sorted out.”

He went on to express disappointment that the PGA Tour would ever get to draw up its own rules, even though their views are canvassed by the R&A and the USGA when changes are made in the first place.

“The PGA TOUR and European Tour guys [officials], they're the best,” Bradley said. “They're just there to relay the rules to us, but some of the things I can't quite figure out. I mean it's different, but I guess the USGA makes the rules, and we got to follow them, and maybe someday that would change, but I highly doubt it.”

Bradley and Westwood led by four strokes from Billy Horschel, Jhonattan Vegas, Francesco Molinari, Kevin Kisner, Roger Sloan and last week’s Honda Classic winner Keith Mitchell.

But it was a tougher day for McDowell who needs a top 10 finish to have any chance of clinching one of three exemptions for Royal Portrush via The Open Qualifying Series this week.

The Portrush native (39) hit just seven fairways in a three-over 75 last night and slipped three outside the top 10 as Lowry made a costly triple bogey at the third (his 12th) to go four-over and after briefly giving himself hope with a birdie at the fourth, dropped three more shots in his next four holes and shot a 79 to finish on five-over.

Two-over for the day through nine, he was still level par for the tournament with seven holes to play before disaster struck.

The HSBC Abu Dhabi Championship winner missed the third fairway to the right and playing from the rough, found left water with his approach, running up a seven.

After taking a penalty drop, he missed the green from 100 yards, chipped to five feet and missed the putt to find himself three-over for the tournament and two shots outside the cut mark.

He rallied with a birdie four at the fourth but three-putted the fifth from 35 feet, coming up short with his first putt, and then went for broke from 250 yards at the par-five sixth but tugged his approach into the lake and made six.

Now six-over, he made another bogey at the eighth, where he could not chip and putt for par from just short of the green and posted his highest score on the PGA Tour since he shot 79 in the third round of the Masters three years ago.

On the European Tour, Gavin Moynihan missed the one-under par cut by a stroke after a rollercoaster day in the Commercial Bank Qatar Masters.

The Mount Juliet professional eagled the 18th to race to the turn in four-under 32 and move into the top-10 on five-under.

But he made five bogeys in seven holes in a homeward 41, carding a 73 to miss out on the weekend action at Doha Golf Club.

South Africans George Coetzee and Justin Harding and France’s Mike Lorenzo-Vera each fired four under par 68s to lead by one stroke from the chasing pack on eight-under.

Team Ireland's Neil O'Briain shot a four-over 76 to miss the two-over cut by two strokes in the Sunshine Tour's Limpopo Championship.

But it was a good day for Leona Maguire in the Symetra Tour's SkyiGolf Championship at Charlotte Harbor National Golf Club in Florida. 

The Slieve Russell star (24) found her putting touch and made five birdies in a three-under-par 69, leaving her just six strokes behind leader Allison Emrey on two-under.

“It takes a while to adjust 16 hours,” she said of her jet-lag following her marathon journey from Australia. “But I am hitting the ball well but putted better today.”