Rory McIlroy is feeling good about his game a month before the Masters but he was left to rue a bad start and an untidy finish as the unheralded Kurt Kitayama snatched the Arnold Palmer Invitational at Bay Hill.

The Co Down man, who needed to win to reclaim the world number one ranking, took the lead on the 13th but played the last five holes in one over en route to a  rollercoaster 70 that left him one stroke behind the winner, tied for second with Harris English (70) on eight under.

While he had a chance to get to nine under with a birdie at the 18th, McIlroy missed a 10-footer on the low side before 30-year-old Kitayama recovered from a triple bogey at the ninth when he birdied the par-three 17th to take the outright lead, then made a brilliant closing par to claim his maiden PGA TOUR title and a place in The Open at Royal Liverpool.

The Californian (30) ripped a 194-yard approach from the left rough to 48 feet at the last and brilliantly two-putted for a 72 and cheque for $3.6 million as English and Davis Riley, who shot a final round 66 to tie for eighth place with Trey Mullinax, claimed the other two exemptions for Hoylake.

Kitayama finished on nine-under-par, one clear of McIlroy and English as Patrick Cantlay (68), Jordan Spieth (70), Scottie Scheffler (73) and Tyrrell Hatton (72) all had their chances to win before finishing a shot further back in a tie for fourth on seven-under.  

"It was really hard,” Kitayama said after leaving his lag putting hanging over the lip of the hole at the last. "I'm going to sleep really well tonight.”

He added: "I've always dreamed of winning on the TOUR and to finally do it, yeah, it's pretty amazing. It's pretty unbelievable, really."

McIlroy was disappointed to play the last five holes in one-over par but he heads for The Players this week with high hopes after almost winning for the second time this year with his B game.

"Playing the last five in one over with this jam-packed leaderboard is not going to get it done,” said McIlroy, who admitted he was left to rue back-to-back bogeys at the 14th and 15th and a missed birdie chance from ten feet at the last. 

"I hit a good putt. It just missed on the low side" he said. "If I look back on today the one thing I'll rue is the tee shot on 14.  

"I birdied 13 and got on to 14 tee and I honestly thought I was still like one or two behind the lead. As I was walking to the 14th green, I looked behind me at the scoreboard, and I was leading by one.

"And if I had of known that, I wouldn't have tried to play the shot that I played on 14, which was unfortunate, but I ended up making bogey there and then a bad swing off the tee on 15 and a bogey."

He added: "But it was a good week. I saw some positive signs. Game's rounding into form for the bulk of the season. So I'm, even though I didn't get the win, I'm still pretty happy with how everything went this week."

Just three shots behind Kitayama overnight, McIlroy's chances of a second win at Bay Hill looked slim when he bogeyed the first and second to slip back to tied 12th and five shots off the lead.

Texan Jordan Spieth led the pursuit of Kitayama with four birdies in his first five holes giving him a share of the lead.

But McIlroy never went away and while he was still five shot behind Kitayama as he approached the turn, he made four birdies in a five holes to find himself in the solo lead.

Kitayama gave the chasing pack encouragement drove out of bounds by inches and triple bogeyed the ninth as McIlroy followed a birdie at the same hole with further birdies at the 10th, 12th and 13th to get to nine-under.

He was briefly tied for lead with Spieth before the Texan bogeyed the 14th, 15th and 17th to finish two shots behind Kitayama on seven-under.

McIlroy would also bogey the par-three 14th to find himself briefly tied with Spieth and Kitayama on eight-under, just one clear of  Cantlay, Scottie Scheffler, Viktor Hovland and English.  

He then found heavy rough at the 15th and dropped another shot to slip one behind Spieth and Kitayama but while he would regain a share of the lead with Kitayama after a two-putt birdie at the par-five 16th, he couldn’t birdie the last. 

He hit his second to 10 feet but missed his left to right breaking putt on the low side and Kitayama would take advantage, rolling in a 14 footer for birdie at the 17th before hitting a stellar approach and an even better lag putt at the 18th.

"Look, I still wish I could have had a couple of shots back today," McIlroy said. "But I guess everyone would say the same thing. 

"It's one of those days and one of those courses where you're going to rue missed opportunities and a couple of missed putts here and there.

"But, yeah, look, again, I need to take the positives from it, which there is a lot of, we've got a massive event next week, and try to bring that momentum into Sawgrass.

"I mean with PLAYERS, Match Play, and then the Masters, so two tournaments between now and then and plenty of time to feel a bit more comfortable with where everything is."

It was a mixed week for the rest of the Irish with veteran Pádraig Harrington (51) the best of the bunch in a tie for 53rd on two-over after a closing 75.

Shane Lowry recovered from a third-round 80, his highest score in the US as a professional, by carding a one-under 71 that left him 67th on five-over.

It was the first time Lowry made the cut in five starts at Bay Hill but he admitted it was still a puzzle for him, tweeting a picture of him and caddie Darren Reynolds sizing up a shot and commenting: "Still trying to figure Bay Hill out."

As for Seamus Power, the West Waterford man followed an opening 72 with rounds of 74, 76 and 78 to prop up the leaderboard in 72nd place on 12-over.

The finale was another good week for the PGA TOUR’s designated event model with many big names at the top of the leaderboard on a dramatic final day.

“Yeah, I certainly felt it on the golf course, so I'm sure it was pretty good to watch,” added McIlroy, who will play the Player and the WGC Dell Technologies Match Play before the Masters.

“It's hard because the lead's changing hands with guys making bogeys, not really making birdies. So don't know how people find that entertainment value.

“But it was a great back nine. It was great to be involved with. I'm really happy for Kurt. He's been playing well for awhile now and I'm happy to see him get his first win.

“I think he's been playing pretty well. I sort of know Kurt more from European Tour stuff because he played over there.

“But he's done really well. He's sort of persevered and played wherever he could get starts and all of a sudden he's won one of the biggest events on the PGA TOUR. So good for him.”