Rory McIlroy's caddie has praised the Northern Irishman for his hard work following his victory in the USPGA Championship.

The 23-year-old recorded an eight-shot triumph at Kiawah Island and JP Fitzgerald claims that the performance was inevitable following a period of bad form earlier in the summer.

"I called it at The Open. I said the way this guy is hitting the ball he is going to destroy fields," Fitzgerald said. "He was playing that well in practice, I knew if it wasn't going to be that week it would happen soon."

Fitzgerald was also delighted with the intensity shown by McIlroy in the final round despite seeming to have had the tournament wrapped up halfway through Sunday's play.

"We got to seven clear standing on the 18th and Rory said to me: 'We won our last Major by eight — let's do it again'," he added.

McIlroy is now top of the world rankings following the win in South Carolina.