Since the inception of the Players Championship in 1974 no player has successfully defended the title, with only six managing to win the prestigious event more than once.
Day’s prospects of creating history looked bright when he played his first 11 holes in five under par, but the 29-year-old Australian bogeyed three of his last four holes and had to settle for an opening 70.
“To be honest I’m not that disappointed,” said Day. “I played some good golf. Six, eight and nine were the only bad holes I played and they weren’t really that bad, but the rest of the game was pretty solid, so I’m pretty happy with it.
“It would be nice to be the first in history [to win back-to-back], but it’s day one, it’s going to be hot tomorrow and play tough the next three days, so I just have to slowly inch my way up the leaderboard and hopefully be in there Sunday.”
Day’s victory at Sawgrass 12 months ago was his seventh in 17 events, but he has recorded just one top-10 finish in 2017, although his form has been badly affected by his mother’s battle with lung cancer.
The former US PGA champion broke down in tears after withdrawing from the WGC-Dell Technologies Match Play in March, just six holes into his opening match.
Two days later his mother Dening successfully underwent surgery to remove a “three-to-four-centimetre” mass in her lungs and Day returned to action in the Masters, finishing in a tie for 22nd at Augusta National.
Day added: “The desire is starting to come back to try to reach the top again. A few distractions earlier this year kind of derailed that a little bit which is understandable, I had to be there with my mum, and now I’m ready to focus on my golf.”
After starting on the back nine, Day had birdied the 11th, 13th and 16th to reach the turn in 33, before holing from 65ft across the first green.
Another birdie on the second took him into the outright lead, only for dropped shots on the sixth, eighth and ninth to leave him three shots behind clubhouse leader William McGirt, who eagled the 11th and 16th in his 67.
McGirt enjoyed a one-shot lead over compatriot JB Holmes and Sweden’s Alex Noren, with Italy’s Francesco Molinari and former Open champion Louis Oosthuizen part of a large group on three under.
Russell Knox, meanwhile, saw his hopes of making a good start at Sawgrass dashed by five bogeys as the Jacksonville-based Scot, pictured, struggled to an opening 76. Knox grabbed just a solitary birdie at the par 5 11th to finish a frustrating day at four over par and well down the field.
Masters champion Sergio Garcia and Rory McIlroy were among the later starters and Garcia had just four players below him on the leaderboard after taking 40 shots to cover the front nine.
That included a double bogey after four-putting the fifth, the same hole the 2008 champion six-putted in the third round last year.
McIlroy, who is playing his first tournament since getting married and signing a multi-million pound equipment deal with TaylorMade, was level par after two bogeys and two birdies on the front nine.
Playing partner Dustin Johnson was also level par, the world No 1 following a bogey on the first with a birdie on the fourth.