Colin Montgomerie has admitted that he is surprised at the speed in which Rory Mcllroy has installed himself as the best golfer in the world.

Mcllroy moved to the top of the rankings after victory at the Honda Classic in Florida, but Montgomerie has hinted that the 22-year-old faces a fight to stay there.

"I thought it would take a lot longer than it has, but it didn't even take another major. He could be No 1 for a while, but you've also got Luke Donald and Lee Westwood and Tiger Woods is as determined as ever. He doesn't like being outside the top 10," Montgomerie told Sky Sports News.

Montgomerie led the European team to victory in the 2010 Ryder Cup.