Graeme McDowell believes Rory McIlroy can win as many major titles as he wants, as long as he remains healthy and motivated.
McIlroy claimed his second major in the space of four weeks and fourth of his career in the US PGA Championship on Sunday, becoming the first player to win back-to-back titles since Padraig Harrington in 2008.
The 25-year-old is the third youngest player behind Tiger Woods and Jack Nicklaus to win four majors and will travel to Augusta next April seeking to complete the career Grand Slam, not to mention remaining on course to hold all four major titles at the same time.
Woods is the only player to achieve that feat by winning the US Open, Open and US PGA in 2000 and the Masters in 2001.
"It's beginning to look a little Tiger-esque I suppose," McDowell said of McIlroy's winning streak, which includes a first World Golf Championship event sandwiched between the Open and US PGA.
"I said at the Open I didn't think we were going to see someone creating their own kind of Tiger-esque era just yet. I'm not eating my words but guess you could say I'm certainly starting to chew on them right now. When the kid is playing well, he's pretty tough to live with. It's pretty special stuff."
McIlroy admits that his split from fiancee Caroline Wozniacki has proven to be good for his golf, winning the BMW PGA Championship at Wentworth just days after calling off their wedding and reaping the rewards of making golf his number one priority.
"He says that he's sort of tied up a lot of his loose ends off the golf course," McDowell added of his former stablemate. "Loose ends is not a very nice term to put your personal life and I don't mean it like that, but he seems to be in a very good place.
"He's an incredible player and when he's in this type of mood, he's pretty tough to beat."
Asked if McIlroy could match Woods' total of 14 majors or the 18 of Jack Nicklaus, former US Open champion McDowell added: "Not many people are born with the type of focus Tiger Woods had, growing up with pictures of Jack Nicklaus on his wall and wanting to beat Jack's record.
"Knowing Rory as I have the last few years, it didn't seem to me like he was trying to beat Jack's record. So it's a case of how the guy continues to motivate himself. You don't know what the number is. It's however many he wants. He'll win as many majors as he wants, within reason.
"Rory has obviously got himself in amazing shape physically now as well and it's just a case of how fit and healthy he can stay. No doubt the game is more physical now. We are seeing more withdrawals and back injuries and neck injuries and stuff going on with guys than we ever have.
"To me, it's 10 per cent staying healthy and 90 per cent how many he wants to win."