Tim Henman paid tribute to Andy Murray for an "incredible" career and explained that his fellow Briton will not want to keep playing just to make up the numbers, amid his impending retirement.
Murray, 31, has been unable to play regularly since his 2017 Wimbledon quarter-final defeat to Sam Querrey, struggling to cope with a worsening chronic hip injury, for which he had surgery.
The three-time grand slam winner has confirmed next week's Australian Open could be his last tournament as the pain becomes too much, and even in a best-case scenario he will only go on as far as Wimbledon.
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"It is sad news, but it doesn't detract from what an incredible career he has had," Henman, who was replaced by Murray as British number one in 2006, said to BBC Sport.
"His achievements - there are no greater goals you can achieve in our sport.
"He feels he can play to a decent level but when he has been contending for grand slam titles and number one rankings he doesn't want to be there making up the numbers."
Comparing it to his own retirement, Henman added: "After Wimbledon in 2007 I started on the American hard-court swing and felt for the first time I was making up the numbers.
"I felt that wasn't what my career was about and I think Andy has said similar things. If you're not improving, your ranking is going to go one way and I always believed I was playing in tournaments to win those tournaments."
Henman added: "It has been heading in this direction. I know how hard he has been working. With the amount of work he has put in, and we know how professional and diligent he is, 20 months is a long time.
"And with the nature of the injury there were a lot of people who said this was going to happen at some stage. He will have ticked every box to give himself the best opportunity to play pain free at the highest level again.
"But the reality is he won't be able to do that. In professional tennis terms he has seen there isn't a fix for this hip problem."
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Fellow Briton Sue Barker, who won the French Open in 1976, sympathises with what Murray has to come to terms with, having struggled with her own retirement in 1984.
"You want to do it on your own terms - not to be forced out because your body breaks down," she said. "I had to quit because of injury and I was crying for weeks. I used to wake up in the morning and think, 'What am I getting up for now?'.
"Every day had been planned around tennis, whether it was training, nutrition, playing, or travelling, it was my passion. I loved my career, and so I know for Andy it is going to be devastating.
"That is why he is so emotional about it because suddenly something that has been a huge, huge part of your life has been taken away, and I'm not sure how you ever replace that. It's such an incredible, wonderful job to have."