A man transformed, Shane Lowry – who admitted to suffering what he termed "a meltdown" in practice on the eve of The Players – turned from frustrated player to a master practitioner in shooting a record back nine of 29 strokes en route to an opening round 65, seven under par, to manoeuvre into contention.

World number one Jason Day's course record-equalling 63 contained nine birdies and nine pars and enabled the Australian to grab the clubhouse lead. Day's error-free round gave him a two-stroke lead over the quintet of Lowry, England's Justin Rose and the American trio of Cameron Tringale, Brendan Steele and Bill Haas on a day of little wind and fine scoring.

But Jordan Spieth – playing for the first time since his Masters collapse last month – suffered a double-bogey seven on the Par 5 ninth, his finishing hole. Asked what had happened, he quipped: “ I hit it seven times.” He signed for a level par 72.

World number three Rory McIlroy was nine shots off the lead after a 72 containing two birdies and two bogeys, the 27-year-old finishing alongside Rickie Fowler after the defending champion carded a double bogey on the 18th. Graeme McDowell and Pádraig Harrington, both out in the tougher afternoon conditions, also shot level-par 72s.

Day’s 63 was a remarkable 18 strokes better than his second-round 81 a year ago when he missed the cut for a third time in five appearances on the Pete Dye design.

“I was under par going through my first nine but there were guys at seven under when I was five under and I’m there going, ‘Okay, I’ve got to keep pushing. When you see someone up the leaderboard distancing themselves away from the field, you’ve got to do something to catch up to them,” said Day.

Lowry, bouncing back from a missed cut in the Wells Fargo at Quail Hollow last week, turned in level par before lighting a fuse that ignited his play on the homeward stretch.

Lowry’s run of birdie-eagle-birdie-birdie from the 10th was sensational and far removed from the frustration he endured in his final practice round on Wednesday. The Offalyman was so at odds with his game and his swing that it took some calming words on the phone in “an emergency call” with his coach Neil Manchip and a piece of live advice from Graeme McDowell to rectify matters.

Of that “meltdown,” Lowry recounted: “I was losing the head (in practice). I was like almost thinking, ‘what’s the point being here?’, because I felt like I was playing poorly and I was struggling on the greens.”

He added: “I’m very much a confidence player, highs and lows are a bit too much at times. But, yeah, when I get it going I’m normally quite good. Sometimes I can get very hard on myself and beat myself up. So, it’s just trying to get somewhere in between.”

A word in the ear from McDowell – who was playing the practice round with him – provided a light bulb moment. “I got a little tip from G-Mac (in practice) and it seemed to help me. Hopefully I can carry that forward and do all the right things come the weekend. I was just getting over the ball a little too close and he just told me to move it an inch away from where it was and see how it feels. For some reason, it just felt easier to see my lines.”

There was no evidence of Lowry’s transformation on a front nine that saw him merely treading water with one birdie and a bogey to turn in level par. On the back nine, however, he opened his shoulders, found his targets and, most critically of all, got the putter working as he rolled in birdie putts and, on occasion, par saves to leapfrog through the field.

On the 10th, Lowry rolled in a 35-footer for birdie that gave him a pep in his step. From there, he moved into a zone. He eagled the 11th, rolled in a five-footer for birdie on the 12th and another from six feet on the 13th.

On the Par 5 16th, Lowry putted from off the front of the green for a tap-in birdie and, after failing to convert a birdie chance from 10 feet on the famed island hole, where he’d hit “a hard sand wedge from 124 yards” off the tee, he then ripped a 332 yards drive down the 18th and put his sand wedge approach to 15 feet and sank the birdie putt to finish in style.

On being told he was the first player to shoot 29 on the back nine, Lowry remarked: “It’s probably as good a golf course as we play all year. It’s a proper test of golf. And to go out and do it on that nine was nice.”

His score was all the more remarkable for the low expectations he carried into the tournament, missing the cut at Quail Hollow and struggling in practice on Wednesday. “I kind of was coming out thinking, ‘if I can just get four rounds in here it will be a big help for (the Irish Open) next week. So, I’m on my way to getting four rounds in anyhow . . . next week’s a massive week for me. This week is big as well, but I’d love nothing more than to go back next week and win a tournament.”