Jason Day went wire-to-wire as he claimed the Arnold Palmer Invitational by one stroke, though the world number three was forced to dig deep on Sunday.

Day had been in control throughout the tournament but he required a final-hole par putt for a two-under-par 70 to make sure of his first PGA Tour title of the season and eighth overall, ahead of Kevin Chappell.

The Australian was in the rough following his tee shot at the 18th and then found the bunker, 30 metres from the pin, as Chappell watched from the clubhouse following his final-round 69.

However, Day - who struggled on the front nine having bogeyed three of his opening six holes at Bay Hill - kept his cool, chipping close to the pin before converting the clutch putt to close out the event at 17 under.

Last year's runner-up Henrik Stenson finished tied for third, having endured a mixed day on the back of four birdies and three bogeys for a one-over-par 71 in Orlando, Florida.

The Swede was joined by Troy Merritt (71) at 14 under after he produced an impressive performance to remain in the hunt throughout the day.

Merritt was largely flawless on the back nine, birdieing his first five holes, but he came unstuck at the 18th after finding the water.

Zach Johnson (68) earned sole possession of fifth, five shots behind Day.

A stroke further back was Kiradech Aphibarnrat (65), as well as Hideki Matsuyama (67) and Jamie Lovemark (70).

In-form Australian Adam Scott (69) was unable to win a third successive tournament after he finished eight shots behind his countryman, while Rory McIlroy (65) was six under at the close of play.