Rory McIlroy watches his tee shot on the fourth hole during the third round of the Arnold Palmer Invitational. Photo: Phelan M. Ebenhack/AP Photo

MIAMI England's Matthew Fitzpatrick fired a bogey-free five-under par 67 Saturday to seize a one-stroke lead over defending champion Rory McIlroy after the third round of the US PGA Arnold Palmer Invitational.

Fitzpatrick, a 24-year-old seeking his first US PGA title after five European Tour triumphs, stood on nine-under 207 for 54 holes at Bay Hill in Orlando, Florida.

Four-time major winner McIlroy, who would complete the career Grand Slam by winning next month's Masters, fired a 67 to join pal Fitzpatrick in Sunday's final pairing.

"It'll be a fun day," Fitzpatrick said. "I've become good friends with him. He has got a ton of fans over here. It's exciting. I've put myself in a good position. I'm looking forward to it."

Australia's Aaron Baddeley, England's Matt Wallace and American Kevin Kisner shared third on 209 but McIlroy, who began the day seven adrift, said plenty of rivals are within reach of the title.

"It's so bunched," McIlroy said. "I'd still say the 2- and 3-unders still have a chance to win the tournament."

World number 44 Fitzpatrick, never better than a share of seventh in a US PGA event, opened with a nine-foot birdie, added a three-footer to birdie the par-5 fourth, began the back nine with a 10-foot birdie putt and added two more at the par-4 15th from 13 feet plus a tap-in at the par-5 16th.

"Just played really smart," said Fitzpatrick. "I've been driving it pretty solid all week. Did the same today. Hit a lot of greens. You've got to play smart and stick to your shots and hit the greens. It's getting harder out there."

Northern Ireland's McIlroy birdied four of the first six holes and three of the last our holes while taking his lone bogey at the par-4 eighth.

"I've just been trying to play high cuts into every single pin I can look at. It's the only way I feel like I can stop the ball near the pin," McIlroy said.

"I knew the key for me today was to hit fairways. The greens are so pure. Whenever you start them on line they have a good chance."

Sixth-ranked McIlroy put his approach to five feet and made birdie at the par-3 second then sank an 11-foot birdie putt at the par-4 third.

After a three-putt par at the par-5 fifth, McIlroy sank a 26-foot birdie putt at the fifth and then blasted from a greenside bunker inches from the cup on the way to a birdie at the par-5 sixth.

He escaped nine with a par after "probably the worst mud ball I've ever had... it was good to get away with a four there."

McIlroy's ferocious finish saw him sink short tap-in birdies at 15 and the par-5 16th then sink a nine-foot par putt at the par-3 17th and drop a birdie putt from the same distance at 18.

"It was nice for that one to go in to cap off a really good round," McIlroy said.

- Friday leaders fade -

McIlroy has not won since taking last year's crown at Bay Hill, his 14th career PGA victory.

"This golf course has played much tougher from the beginning compared to previous years," McIlroy said. "The course is going to get tougher as it goes along.

"The greens are getting so firm and so fast out there, anything above the hole you're going to have trouble getting it to stop."

McIlroy won major titles at the 2011 US Open, the 2012 and 2014 PGA Championship and the 2014 British Open.

Second-round co-leaders Keegan Bradley of the United States and Tommy Fleetwood of England faded, Bradley firing 75 to finish three back and Fleetwood shooting 76 to stand four adrift.

AFP