Eighteen-times grand slam champion Evert was engaged to fellow American tennis champion Jimmy Connors in 1974, the year both won the Wimbledon title, but the so-called golden couple cancelled their wedding.
McIlroy, twice a major champion, announced on Wednesday that he had changed his mind about marrying Dane Wozniacki despite the wedding invitations having already been posted.
"It doesn't surprise me," Evert, who was 19 when engaged to Connors, said in an ESPN conference call ahead of next week's French Open.
"I look back at Jimmy and I. To look at two players that are in the prime of their career and are striving to be No. 1, (you) don't see each other.
"I mean, I was married in my 20s to my tennis. That was the only way I could put all my emotions and energies into that goal. I was in awe that it (McIlroy and Wozniacki's relationship) worked as long as it did.
"I can't believe it. They must be just different kind of people. I understand 100 percent, you're married to your career. You're using your emotions. You're using the mental capacity that you have.
"You're putting everything into it. That's what it takes to be the best."
Evert has since been married three times, to former British tennis player John Lloyd, downhill skier Andy Mill, with whom she had three sons, and Australian golfer Greg Norman -- all of them ending in divorce.
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