Montgomerie and Harrington, who boast nearly 70 professional wins between them, discuss McIlroy's prospects in an interview to be broadcast on BBC Radio 5 live on Thursday.
They say they expect the 24-year-old to continue his assault on golf's record books, despite his difficult 2013.
Montgomerie, winner of a record eight European Tour Order of Merit titles, maintains the Northern Irishman is too good not to start winning again on a regular basis.
"He's the most talented player to emerge since Seve Ballesteros," said Montgomerie. "Seve fell out of his pram playing golf and Rory did the same thing. That's not going to go away."
McIlroy failed to win in 2013 until his penultimate event, the
Australian Open in December,
but Montgomerie does not foresee similar struggles in 2014.
"I think it was a blip year," said the Scot. "A lot was happening and I think Rory will get back to winning ways."
Three-time major winner Harrington also anticipates a rapid revival.
“The trouble with Tiger is that he just has not been aggressive enough over the weekends. He has played safe golf, he hasn't attacked.”
Montgomerie on Woods
"I've said it is possible Rory could compete with Jack's record," said the 2007 and 2008 Open champion. "Time is on his side. He started winning majors at 22, so that gives him a good bit of time.
"Rory has won two in the last three years. That's a good stat. If he wins more in the next three years, then that really becomes some stat."
As for Woods, Montgomerie believes this is a crucial year if the 14-time major champion is to overhaul Nicklaus's record. The Scot points out that the world number one, who has not won a major since 2008, has previously won at three of this year's major venues.
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