Europe's Ryder Cup winning captain Paul McGinley believes Rory McIlroy still has a lot of work to do if the world No.1 is to match the legacy left by Tiger Woods.
McIlroy heads to the Masters this week with hopes of completing a career grand slam. The Ulsterman enjoyed successive major victories in 2014 and a Ryder Cup win at Gleneagles, but McGinley says Woods' haul of 14 majors is still a long way off.
"Rory's not the finished article," McGinley told The Times. "He still has a long way to go to meet the standards that Tiger set.
"The biggest challenge Rory has got is keeping the fire lit in his heart. That's what made Tiger phenomenal. At the moment he has it and he's had it for a number of years, but keeping it lit for another 20 is another question."
McIlroy has not enjoyed the best of times at Augusta National. The 25-year-old recently admitted his 2011 meltdown, in which he led by four shots heading into the final round only to blow his chances with an 80, was the "most important day of his career".
Having managed him at Gleneagles, McGinley admitted McIlroy's patience has improved since that fateful day at Augusta - but there is plenty of room for improvement.
"If he wants to evolve to the heights that Tiger set, he has to improve on his level of patience," McGinley added. "Jack Nicklaus said winning a major championship [involves] a high dependency on being patient. Rory is more patient than he was two years ago but still has a way to go.
"Rory is a streaky player and when he gets hot with the putter he holes his percentages. When he finds that extra gear nobody can match him.
"It will be a matter of time before someone catches up with him. Tiger Woods had that [aura] and then guys caught up with him."