Day, the 2015 PGA Championship victor, held off Americans Aaron Wise and Nick Watney with a final-round two-under par 69 to finish 72 holes on 12-under 272 for a two-stroke victory at Quail Hollow in Charlotte, North Carolina.
Woods moved up 17 places on the leaderboard on Saturday with his first round in the 60s at 68 to sit at 1 under for the tournament, but still was not pleased with the flat stick that has left him confused on the greens at Quail Hollow Club. Mickelson started firing at flags and made six birdies, but finished five shots back after a 69.
Day did his part with five birdies on his last 10 holes and a daring shot on the 18th when he stood barefoot in the creek to play a shot onto the green.
"I had no idea where the ball was going today, especially off the tee, " he said. "Hit some good drives that just ended up off the fairway, some landed in the fairway, so I wasn't disappointed with that". "First low round of the year, I feel like, and I have to go (urinate) in a cup".
A birdie at 10 extended Day's lead to three but consecutive bogeys at 13 and 14 after errant tee shots saw Day fall level with a fast-finishing Wise.
Five-time major victor Phil Mickelson fired a 64 to stand 10th on 208, one stroke behind South African Charl Schwartzel and Americans Johnson Wagner and Sam Saunders.
Woods said he was looking forward to the opportunity to play with Mickelson. I just didn't hit good putts, and on top of that, the ones I did hit well, I didn't have enough speed on them. 5 and 6. Although he rebounded with birdies at the seventh, eighth and 10th holes, he faltered again with another bogey-bogey stretch at Nos.
That's when Woods challenges the tour's top talent at The Players Championship. "This is probably one of the best wins I've ever had, just because of how hard everything was today".
"It was on a cracking line, it was handsome", Day said. "You're going to fail, you're going to fail, '" Day said.
But you may be wondering, as I did, where has Watney been over the last few years on the PGA Tour?
"I feel like I'm hitting the ball well enough and I'm trending in the right direction for next week".
"I'd like to be able to hit it a little bit straighter", he said. "The '97 Masters and the 2000 U.S. Open, I didn't miss one like that under 10 feet for the week", Woods said.