Serena Williams is hoping to return to the women's tennis tour by early summer following a serious health scare.

The 13-time Grand Slam champion underwent emergency surgery, earlier this week, after a blood clot was discovered in her lung. Williams suffered a pulmonary embolism last week before this second problem was spotted by doctors.

The 29-year-old former number one is cautiously optimistic on a return to the game -  which is great news for both fans and collectors. Tennis based collectibles are a burgeoning market for alternative investors.

We've speculated before on how its memorabilia is likely to come into its own, and in recent times items have been key draws in sports memorabilia auctions, including items related to stamp collector Maria Sharapova.

The longer Serena can keep winning, the more valuable her collectibles are likely to be in the long run.

In the short term however, it remains possible to pick up fascinating items from great champions such as Björn Borg at a fraction of the cost of other sports.

This signed photo of Bjorn Borg is available for £395 (Click here for more details)

"While I can't make any promises now on my return, I hope to be back by early summer. That said, my main goal is to make sure I get there safely," Williams said in a statement.

She added that the experience had been "extremely hard, scary, and disappointing".

Williams has been one of the game's leading stars for more than a decade and along with sister Venus has been instrumental in the development of a more powerful women's game.

Serena Williams won her first Grand Slam title at the US Open in 1999

Williams has not played in a tournament since winning Wimbledon last year. She has been beset by injury of late, including a cut foot inflicted by a piece of broken glass at a restaurant.