Orlando, FL (SportsNetwork.com) - Morgan Hoffmann fired a 6-under 66 in Thursday's opening round of the Arnold Palmer Invitational and he leads by one stroke over five players.

Hoffmann is winless on the PGA Tour. He finished third at the BMW Championship last September for his best career finish.

Ian Poulter and Kevin Na both carded 67s on Thursday at Bay Hill Golf Club and Lodge. They were joined in second place at minus-5 by Ken Duke, Jason Kokrak and John Peterson.

Henrik Stenson and Adam Scott, world Nos. 3 and 4, shot 4-under 68 in the opening round. They share seventh place with defending champion Matt Every, Honda Classic winner Padraig Harrington, Hunter Mahan, Brandt Snedeker, 2011 winner Martin Laird, reigning FedExCup champ Billy Horschel, last year's runner-up Keegan Bradley, Ben Martin and Harris English.

World No. 1 Rory McIlroy, who is playing this event for the first time, posted a 2-under 70. He is among a large group tied for 32nd.

McIlroy opened with five pars in a row. He 2-putted for birdie on the par-5 sixth and rolled in a 17-footer for birdie at the eighth. After seven straight pars, McIlory found water with his second at the par-5 16th.

That led to his only bogey of the day. McIlroy atoned for that mistake with a 14-foot birdie putt at the 18th.

"I felt like I was seeing good signs out there with my game. I hit a lot of good shots. I was trying to stay as patient as possible. I was hitting good shots and not really doing anything with them," said McIlroy. "I was a little disappointed with how I played the 16th hole, but positive signs."

Hoffmann started on No. 10 and he poured in a 33-footer for birdie on his opening hole. He moved to 2-under with a birdie at the 12th.

The 25-year-old ran off nine consecutive pars from No. 13. Hoffmann tapped in a short birdie effort at the fourth.

Hoffmann found a greenside bunker with his second at the par-5 sixth. However, he holed his bunker shot for eagle. That moved him into a share of the lead. Hoffmann closed his round with a tap-in birdie at the ninth.

"It's crazy how this game works. I've been grinding really hard since last weekend. Missing the cut in Tampa put a spark under me, and I worked hard on my ball-striking and it paid off," Hoffmann said.

Poulter converted back-to-back birdies at four and five. Around the turn, he birdied the 11th. Poulter jumped into a share of second place thanks to a 16- foot eagle effort from just off the green at the 16th. Poulter parred the final two holes to end there.

Na flew up the leaderboard early in his round as he birdied three of four holes from the second. He parred five in a row before stumbling to a bogey at the 11th.

The 2010 runner-up birdied the 15th and 16th to move to minus-5. He closed with a pair of pars.

Duke stumbled to a bogey at the 13th, but he followed that with three straight birdies from the 14th. Around the turn, Duke birdied three of the first five holes to gain a piece of second place.

Kokrak took advantage of the two par-5s on the back nine. He birdied the 12th and made eagle at No. 16 to move to minus-3. Kokrak flew into the lead at minus-6 as he birdied three of four holes from the second. However, he stumbled to a bogey at the seventh to fall one off the lead.

Peterson opened his bogey-free round with three pars in a row from the 10th. He birdied 13, 16 and 18 to head to his second nine at minus-3. Peterson started his inward nine with four straight pars. He grabbed a piece of second place thanks to birdies at five and eight.

NOTES: Hoffmann entered the week ranked 212th in driving accuracy and 205th in greens in regulation, but he hit 12 of 14 fairways and 14 of 18 greens in the opening round ... Kevin Kisner, who replaced Bubba Watson in the field, opened with a 3-under 69 ... Watson withdrew due to the death of a childhood friend.