Rory McIlroy cast a shadow over his defence of this week's Players Championship on Monday after revealing that the back problem which forced his withdrawal from the Arnold Palmer Invitational needed more treatment.
The Golf Channel television network quoted a text sent by McIlroy which said the Northern Ireland star was delaying his arrival at TPC Sawgrass this week to Wednesday.
"The back is being a bit more stubborn that we thought, so I'm staying at home today and tomorrow to continue treatment in South Florida with the hope to travel to Ponte Vedra on Wednesday at some point," McIlroy was quoted by the network as saying.
On Saturday, McIlroy withdrew from the third round of the Arnold Palmer at Bay Hill after feeling a "small twinge" in his back while warming up in the gym.
He later complained of muscle spasms in his lower back after hitting balls on the driving range, prompting his decision to withdraw.
McIlroy's back problem comes at a critical period of the season for the five-time major winner.
He had been hoping to defend his Players crown in Florida this week before turning his attention to the defense of his Masters title at Augusta next month.