Rory McIlroy
Rory McIlroy storms away after hitting his ball into the water on 18. [Reuters]

Rory McIlroy has pulled out of the Honda Classic in Florida on day two with his card showing seven-over after seeing his game completely fall apart.

The defending champion had posted par after the first round but he never looked settled and on Friday he endured a nightmare start to the round before storming off the course and quitting the tournament.

The world number one started at the 10th and had immediate problems as he double-bogeyed 11, bogeyed 14, triple-bogeyed 16, bogeyed 17 and then put his second shot at 18 in the water.

Having taken a drop, McIlroy pitched to the green but at this stage simply walked off the 18th fairway without taking his putt and reportedly got straight into his car and drove away from the course.

McIlroy has struggled to find his form in the early part of the season but after going round in par on Thursday he felt he was steadily finding his swing.

"I felt like I hit the ball OK today, not as good as I can, but it's getting there," McIlroy had said after the first round.

However, after clearly struggling to find any sort of rhythm on day two, McIlroy said: "There's not much I can say, guys. I'm just not in a great place mentally."

McIlroy had looked unhappy all day long as he uncharacteristically threw his clubs away in frustration and it became clear that was becoming upset.

It has been a difficult few weeks for McIlroy as he missed the cut for the first event of the season in Abu Dhabi and was then knocked out of the Accenture Match Play in the opening round.

This is all since the 23-year-old became the new face of Nike gold when he signed a deal worth around £150million over 10 years.

McIlroy has been forced to defend his form since signing the new contract as he made it clear that it is never easy making a big change.

"It's an adjustment period. It is more about how I'm swinging the club. That's the real concern. It's a little bit mental, but it was more physical [with my swing].," said McIlroy.

"The biggest thing was finding a driver that suited me and I feel like I've got one now that really works. I just need tournament rounds to get that confidence in it."