On the surface, the announcement itself is not surprising. But it could be a warning about Maria Sharapova's tennis shelf life approaching its expiration date.

Sharapova's agent, Max Eisenbud, announced last weekend that Sharapova, who will be 29 in April, is done with Fed Cup competition for her career. The No. 6 player in the world, who is recovering from a shoulder injury sustained during the Australian Open, was scheduled to play only doubles against the Dutch last weekend. But when the Netherlands got the clinching victory before the doubles match was played, Russia substituted Ekaterina Makarova for Sharapova.

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Eisenbud "told Eurosport that this would most likely be the last time that Sharapova represents her country at the Fed Cup," vavel.com reported.

"In order to play, she needs to be healthy," Eisenbud added. "For this to happen, she will need to listen to the voice of her body, to the advice of doctors... But if her health is not good, it is unlikely that she will remain on the tour."

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While that decision sounds logical, it also raises questions about Sharapova's current health. Vavel reported "concerns in Sharapova's camp" about her shoulder injury.

The only reason she agreed to play doubles in last weekend's faceoff was to remain eligible to represent Russia in the 2016 Summer Olympics in Rio de Janeiro.

She is expected to receive treatment on her shoulder in Germany this week to help her return, and there are no reports of her shoulder injury jeopardizing any tournaments in the immediate future.

But if the shoulder injury is such that it will continue to hinder Sharapova's play, how much longer is she interested in competing at less than full strength?

Sharapova lost her 18th consecutive match to Serena Williams, in the Australian Open quarterfinals a few weeks ago, and it would appear Sharapova would need to be at full strength to challenge the No. 1 player in the world.

If the shoulder prevents Sharapova from playing at her top form, then the logical question becomes how much longer she would want to play knowing that it's not her best work. Retirement may not be far away.

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