Wi mixed seven birdies with a bogey on the par-four eighth while the highlight of Dufner's round was an eagle on the par-five 16th thanks to a fine 208-yard approach shot with his four iron to 18 feet for the eagle putt.
For Wi, it was the perfect response to a nightmare final round at the Transitions Championship on Sunday where he took 13 strokes on a par-five hole.
"I didn't really think about that really, that was just a blip on the radar screen," Wi said after his round on Thursday.
Dufner has now held at least a share of the lead during each of the last three events on the Florida swing and the runner-up in last year's PGA Championship is positioning himself as a fascinating dark-horse for the April 5-8 Masters.
The Cleveland-born Dufner went to school in Fort Lauderdale and clearly feels at home on Floridian courses.
"I have played a lot of good golf throughout my career in South Florida, so I feel comfortable here. I'm playing some really nice golf, I am just looking to close a little better on the weekend," said Dufner, who will be 35 on Saturday and has yet to win on the PGA Tour. "I have to try to close one of these tournaments out and try to get a win." Nick Watney (68) was two shots back of the leaders after recovering from bogeys on the second and fourth holes thanks to some smart putting - five of his six birdies were from between eight and 15 feet.
The top six ranked players in the world opted to skip the event but former world number one Tiger Woods and England's in-form Justin Rose were among a pack of seven golfers sitting three shots back of Wi after posting scores of 69.
"I didn't really do anything great today. I was just solid all day," said Woods. "I drove the ball well, hit my irons decent and putted alright. I had two three-putts but also made a couple of bombs out there." Anthony Kim (69), who started on the back nine, had one of the more eventful opening rounds at Bay Hill as his scorecard featured five birdies, a hole-in-one on the 200-yard par-three 17th and four bogeys.
Defending champion Martin Laird was six shots off the pace and in a share of 27th place after mixing four birdies with four bogeys for an even-par 72.
Phil Mickelson, aiming to find his form in time to push for a fourth Masters triumph, shot a one-over 73 with double-bogeys on the third and 18th holes.
"It wasn't the greatest round. I had a middle stretch there of four holes where I played five-over. So I fought back hard to get back to one over," Mickelson told reporters.
"But if I can come out tomorrow and get a hot round, I can get right back in it for the weekend."
