The 36-year-old says the back injury he suffered preparing for his third round at Bay Hill last Saturday is improving.

The Northern Ireland player hit balls on the range on the eve of this week's prestigious event hopeful that he will be able to compete.

"It's better than it was," McIlroy told reporters. "I hit up until a six-iron on the range there and it felt OK."

He withdrew from the Arnold Palmer Invitational after aggravating his back in a pre-round gym session.

"I'm taking it sort of hour by hour. But it feels better. That's all I can say.

"I couldn't stand to address the ball on Saturday morning on the range at Bay Hill, and it's obviously better than that.

"So, yeah, probably a game-time decision, but all indications are pointing in the right direction, so hopefully a good night tonight. The drugs are working wonders."

McIlroy would be bidding to become the second player after Jack Nicklaus to win three Players Championship titles, and the first to win all three at the famed TPC Sawgrass course.

He is also less than a month away from the defence of the Masters title he won at Augusta last year to complete the career grand slam.

McIlroy is confident he would not aggravate the injury were he to play here this week. "It's not structural, it's not joint, it's fine," he said.

"It's purely a muscular sort of discomfort and fatigue. Obviously I'll listen to the professionals. But there's nothing that I can do that's going to harm that."

He added: "Things are getting better, but yeah, I don't think it's something where if I play I'm at risk of doing any damage."

McIlroy made his comments before setting off to walk nine holes to practise chipping and putting, but leaving longer clubs in his bag.

He is due to tee off at 13:42 local time (17:42 GMT) alongside two other major champions, Xander Schauffele and Hideki Matsuyama with rain and thunder forecast for the opening round.