Rory McIlroy has all the capabilities to win any tournament and can complete the career Grand Slam, says the legendary Tom Watson.
Four-time major champion McIlroy has been stuck on three legs since winning The Open in 2014 and three attempts to win The Masters and complete the set since have proved fruitless.
Rival Jordan Spieth, who won last month's Open, has the chance to beat McIlroy to the honour by winning the US PGA Championship at Quail Hollow this weekend.
But McIlroy heads to Charlotte with new-found form as a top-10 finish at Royal Birkdale was followed by a tie of fifth at the WGC-Bridgestone Invitational, having missed the cut at three of his four previous tournaments prior to The Open.
Watson, who like McIlroy has won three of the four majors, acknowledges that in golf there are no guarantees but has no doubt the Northern Irishman has the game to join the elite players to have won all four majors.
"It's hard to say [if McIlroy will do the Grand Slam]," Watson told Omnisport.
"Again it's very difficult to just predict what tournaments you're going to win. He certainly has the capabilities of winning any tournament he plays in and he certainly has two [actually three] legs of the grand slam right now.
"I would expect by the end of his career, he's also a very young man. He will probably complete the grand slam."
On what the field can expect at Quail Hollow, he added: "Quail Hollow players very long and if it gets any type of wind it'll play very tough.
"It's always been a good golf course. I played it a long time ago before they lengthened it and changed it. But it's a real, real good golf course."