O pen champion Rory McIlroy can win up to 15 more Majors and match Jack Nicklaus's haul of 18 titles, says Padraig Harrington.

The two-time holder of the Claret Jug reckons his Irish compatriot can monopolise the game for two decades.

His forecast flies in the face of Graeme McDowell, who doubted whether one man can rule golf the way Tiger Woods or Nicklaus did.

But Harrington is convinced McIlroy - still only 25 - has the tools to reign supreme for as long as his motivation and drive hold out.

"Rory has won three Majors in four years, which is pretty good," says the Dubliner, who also has contributed three to Ireland's tally of eight Major titles since 2007.

He added: "If he continues to win at that rate, he'll have a very successful career. He could be competitive for the next 20 years and that could mean 15 more Majors.

"But there are things we can't foresee. Just because you're good enough doesn't mean it's going to happen. Things happen, injuries for example.

"If Rory is to get to high numbers, it is the next (few) years that will determine it.

"The more years where he wins two or three, that's how you get to 14 ... Tiger had four in a calendar year.

"In 10 years' time (his strike rate) might slow down to one every two years, so he won't be as prolific. Age is on his side, but not necessarily time.

"Rory probably drives the ball better than anybody else in the game. There are some guys longer than him but he is more effective - he hits it straighter and higher.

"He has an advantage and he lives off that advantage because the courses and conditions suit him.

"At the moment, when he plays well, he has stolen a march on everybody else.

"If he's got his 'A' game, whoever is trying to beat him will need their 'A' game to be there with him. Whether that's an Adam Scott or Tiger (Woods), they're going to have to play their very best to compete with Rory."

Harrington says McIlroy "has the ability to go into the Majors as favourite for a long number of years."

But he warned: "The kids in college now are going to learn from Rory and come out with similar games.

"They might not be as good but they will have similarities. There will be more players like him. Tiger had that advantage and it's been eaten up now and Rory's advantage will be eaten up in time, too."

McIlroy's victory at Hoylake has confounded the critics who said he would never win the Open because his game was not suited to a links course.

But he has the high ball flight to cope with Augusta where next year he'll bid to win the US Masters and become only the sixth winner of a career Grand Slam.

McIlroy will play next week's World Golf Championship in Akron, Ohio, and is 6/1 favourite to win the US PGA Championship next month.