Sports stars who won't be at the Olympics

Roger Federer will miss the Rio Olympics with a knee injury. Photo / AP

Swiss medal hopes in tennis are all but dashed as world number four Stan Wawrinka joins compatriot Roger Federer in pulling out of the Olympics through injury.

Wawrinka, who is struggling with a back injury, is pulling out after a medical examination by his doctor in Geneva.

Wawrinka's countryman, 17-time Grand Slam champion Roger Federer, announced last week that he will miss the Olympics and the rest of the season with a knee injury.

The Swiss pair are not the first and might not be the last big names who won't be making the trip to Rio.

LeBron James, Steph Curry, Russell Westbrook, Steven Adams - Rest, Club over country

A number of NBA stars have withdrawn from selection consideration following the end of the NBA season. Adams announced earlier in the year that he wouldn't be part of the Tall Blacks campaign if they did manage to qualify, deciding the focus on next season for the Oklahoma City Thunder. Westbrook, Adams Thunder teammate announced last month he'd also skip the Olympics without citing a reason just saying ""After speaking with my family, I have decided to not participate in this year's Olympics". Two-time NBA MVP Curry stated he is deciding to rest his knee over August. LeBron James also won't be there denying the Olympics two of the biggest name in the sport.

Rory McIlroy, Jason Day, Jordan Spieth, Dustin Johnson et call - Zika, scheduling commitments

Golfers have been the biggest group of athletes to pull out of the Olympics.

Here's the world golf rankings:
1 - Jason Day - Not going
2 - Dustin Johnson - Not going
3 - Jordan Spieth - Not going
4 - Rory McIlroy - Not going
5 - Henrik Stenson - Going
6 - Bubba Watson - Going
7 - Rickie Fowler - Going
8 - Adam Scott - Not going
9 - Danny Willett - Going
10 - Branden Grace - Not going

Lionel Messi - Been there, done that

Messi led Argentina to gold at the Beijing Olympics in 2008 but won't be making the trip to Brazil, where Argentina qualified after winning the 2015 South American Youth Championship. Three overage players can take part in the under-23 tournament, however Messi withdrew from consideration after deciding to concentrate on the Copa America tournament instead.

Mexio's Javier "Chicharito" Hernandez has also taken the same stance as Messi, choosing the Copa America over the Olympics, a decision he probably regrets after Mexico were knocked out in the quarter-finals 7-0 by Chile.

Joseph Parker - New chapter in life

Last month the International Boxing Association announced that professional fighters will be allowed to compete at the Rio Olympics. The rule change won't tempt Kiwi heavyweight champion Joseph Parker however with his team stating he will continue to focus on a potential world title fight against 2012 Olympic champion Anthony Joshua.

John Isner - Rest

After Federer and Wawrinka, Isner is next the highest profile tennis player to pull out from the tennis tournament at Rio saying he wants to rest up ahead of the US Open a month after the Games.

Rafael Nadal is also struggling with injury on the eve of the Olympics.

Nick Kyrgios, Bernard Tomic - Not happy

Aussie Kyrgios accused the Australian Olympic Committee of "unfair and unjust" treatment when he announced he won't be going to Rio following a long-running battle with the committee. Tomic withdrew from the Olympics in May, meaning Australia's top two-ranked tennis men won't be in Rio.