Padraig Harrington believes patience is key to Rory McIlroy winning another major title.
On the eve of the 2018 Open, two-time winner Harrington believes it is only a matter of time before the former world number one ends his majors drought.
The Northern Irish golfer has not won a major since 2014.
"The beauty for Rory is he's still very young, he's still very capable, and with patience those majors will come," said Irish golfer Harrington.
Harrington puts McIlroy's barren run down to increased competition in the elite game but has no doubt the Holywood golfer, who bids for a second Open title at Carnoustie this week, will eventually record another major victory.
Speaking on his return to the scene of his own first Open success in 2007, Harrington said:
"Rory's obviously played well this year and yet seems to be getting a lot of press saying he's not playing so well.
"Clearly, his career is now solely based on how he does in the majors.
"There seems to be no other yardstick for Rory, and that's probably the yardstick he uses himself.
"Back in 2011 he had stolen a march on the field when it came to driving the golf ball, which brought tremendous confidence to his game.
"I think players have caught up. There are many players who drive the ball (to a) comparable (standard) and have certainly eaten into that advantage."
McIlroy tees off in Thursday's first round at the Open at 12:53 BST, playing with Australia's Marc Leishman and Thorbjorn Olesen of Denmark.
Harrington beat Sergio Garcia in a play-off to claim the Claret Jug at Carnoustie 11 years ago, a trophy he retained by winning at Birkdale the following year.
Now, a year after returning to Birkdale, he is pleased to be back at the scene of another past triumph.
"I look forward to playing in every Open Championship," he added.
"This one, like last year, I'm coming back as a kind of defending champion.
"I know Jordan (Spieth) won last year but it does makes it a little more special when you're coming back in that circumstance."
Harrington is in a group with two-time Masters champion Bubba Watson and Matt Wallace which tees off at 14:48.