The 34-year-old Day has been working with instructor Chris Como on a swing that will protect his chronically balky back POTOMAC, Md.: Three years and 364 days since his last victory, Jason Day describes himself as “obsessed” with honing his new swing and improving his results, even if he never gets back to No. 1 in the world. There wasn’t much room for improvement Thursday as Day shot a 7-under 63 to take the first-round lead at the Wells Fargo Championship. Joel Dahmen was a shot back on what could be the best day for scoring at TPC Potomac at Avenel Farm, with rain, wind and unseasonably cool temperatures in the forecast through Sunday. “Obviously, we’ve got some weather coming in, so I feel like we’re going to go into grind mode over the next few days, which I typically like,” Day said. “It’s going to be difficult.” The 34-year-old Day has been working with instructor Chris Como on a swing that will protect his chronically balky back, and he says it feels solid with every club except the driver. His renewed dedication and relative good health are encouraging signs from a player who won eight times in a 15-month span in 2015-16, including the PGA Championship and the Players Championship. “I think about the golf swing in the morning, I think about the golf swing during the day and I think about the golf swing at night,” Day said. “There’s been conversations at 12 at night with Chris just because I have an idea in my head and a certain sensation and a feel.” Day’s last win came in this tournament at Quail Hollow. The Wells Fargo moved to the Maryland suburbs of Washington this year because its usual venue is hosting the Presidents Cup in September. The International team at that event would surely welcome a resurgent Day, who made five of his eight birdies from inside 10 feet on Thursday. The Australian took the lead with a chip-in on the par-4 15th hole. “The thing that’s different between now and when I was No. 1 in the world, even though the technique might not have been as crisp as it is right now, I had all the confidence in the world, especially on the greens. So that’s always the goal,” Day said. Matthew Wolff, local favorite Denny McCarthy and PGA Tour rookies Aaron Rai, Callum Tarren and Paul Barjon were two shots back. Rory McIlroy, the top-ranked player in the field at No. 7, had an up-and-down 67. Wolff’s previous two competitive rounds were an 81 and a 78 at the Masters, where the 23-year-old long-hitter finished behind every 60-something past champion in the field. He played a casual round at his home club a few days ago and lost every ball in his bag. Beware the player with nonexistent expectations. “I can go out and shoot 90 tomorrow and as long as I have a good attitude, I can put a check mark on this week and say that I’ve grown as a person and as a player and that’s just all I really care about right now,” Wolff said. “To be honest, it’s funny, but I’m not here to win a golf tournament, I’m here to have a good time.” Dahmen enjoyed his quick surge to the top of the leaderboard. After a 7-iron from 173 yards to 7 feet on the par-4 eighth hole, he stared at the scoreboard behind the green while waiting for playing partners Patrick Reed and Jason Dufner. Then he holed the putt to reach 6 under. “I like seeing my name up there. It’s something that, you know, that’s what we work for, right? To have a little bit of pressure in the first round I think is great,” Dahmen said. Dahmen’s putter cooled on the back nine, but he finally made another birdie when he missed an ace by inches at the par-3 17th. McIlroy’s only big mistake was a tee shot that started too far left and drew into the water on the par-4 fourth, his 13th of the day. A penalty drop and a sloppy chip led to double bogey, but he rebounded with birdies on the next two holes. “I said to myself walking off the green, if I could just get back to 3 under for the day by the end of the day after that, I would be pretty happy, and obviously I did that,” McIlroy said. Rickie Fowler hit two shots into the right-side wetlands on the par-4 sixth, then holed out from 134 yards to save bogey. He hit driver to 11 feet for eagle on the 305-yard, par-4 13th in a round of 66 that he summed up as “interesting.” “There was a couple that were a little offline and cost me a little bit early in the round, but other than that, a lot of good stuff,” said Fowler, who is working through swing changes and has dropped to 146th in the world. “Definitely happy with today.”