Greg Norman said Rory McIlroy must address his putting "nemesis" in order to return to the peak of his powers as the four-time major winner attempts to end his slump at The Open.
McIlroy has dropped to fourth in the world rankings after failing to win a title this year and will tee off at Royal Birkdale on Thursday amid a poor run of form.
The Northern Irishman has failed to make the cut in three of his last four tournaments and said playing in the wind has been a big factor in his poor form in recent weeks.
Two-time Open champion Norman says McIlroy must improve on the greens in order to have any chance of lifting the claret jug for a second time on Sunday.
The charismatic Australian told Omnisport: "He is struggling at the moment. His self-analysis is he's struggling with his short game. His putting is his nemesis.
"He's never been a consistently great putter for the quality of ball-striker that he is.
"If you look at his putting technique you can see some flaws there, he doesn't develop the confidence because he doesn't have the consistently high level of putting week in, week out. If that starts to slip a bit...
"If you are missing the cut by one shot, you might as well miss it by 10. A player of his calibre shouldn't be doing that.
"He has the capability of turning it on as we have seen many times, if he starts making a few putts in a practice round and gets the confidence going, he can take that in from a Thursday to a Sunday at Birkdale for sure."
Norman also believes McIlroy should learn from his Twitter spat with Steve Elkington by not rising to the bait on social media.
"If you are going to go on social media, you've got to make your point, say what you want to say and don't react." Norman added.
"You let somebody else react, that's just part of it. People feel like they are empowered, whoever it is. Freedom of speech and freedom of social media allows people to attack you and can be pretty vicious.
"I didn't see what was going back and forth with Steve and Rory, but it would be wise for him to back away from it and not make comment. If you're going to go with a fellow competitor, get on the phone and talk about it, not on social media."
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