World number one Rory McIlroy has admitted that he has "no excuse" for walking off during the Honda Classic on Friday.

The Northern Irishman pulled out midway through the second round, citing a severe toothache as the reason for his walk-off.

"I realised pretty quickly it was not the right thing to do. I regret what I did. It won't happen again. There is no excuse for quitting," the 23-year-old told reporters at a press conference.

"At that moment in time I was all over the place and I just saw red. I feel like I let a lot of people down with what I did last week, and for that I am sorry.

"No matter how bad I was playing, I should have stayed out there. I should have tried to shoot the best score possible even though it probably wasn't going to be good enough to make the cut."

McIlroy's poor form has been attributed to a change of equipment.