When Roger Federer and Martina Hingis decided to team up to play mixed doubles at the 2016 Olympics, a Swiss newspaper boasted the country would bring a "Dream Team" to Rio de Janeiro that could sweep all the tennis medals.

Just who else will be on the "Dream Team," though, remains a bit uncertain.

The Olympics may be seven months away, but the jockeying has already begun for the precious few spots available on national teams. While the singles draws will prove fairly straightforward — they'll be based largely on rankings — the men's, women's and mixed doubles fields are much more fluid.

A few pairings have already been decided, including the American twin brothers Mike and Bob Bryan, the defending gold medalists in men's doubles; and of course, Venus and Serena Williams, who have captured the women's doubles gold at three of the last four Olympics.

For everyone else, though, the waiting — and speculation — has just begun.

Rising star Belinda Bencic would seem a perfect fit to play doubles with Hingis for Switzerland. After all, Bencic has been mentored by Hingis' mother since she was a child.

But Bencic said nothing has been finalized with Hingis, who is ranked No. 1 in doubles with regular partner Sania Mirza of India and seems more focused on the Grand Slams at the moment. Hingis and Mirza have already won Wimbledon and the U.S. Open together and they're the top seeds at the Australian Open.

After the duo won their opening round match on Thursday, they were asked whether they would practice or play tournaments with other partners this year to prepare for Rio. "I think at this point we'd be pretty stupid to do that," Hingis replied with a laugh.

Hingis said she's also still trying to decide between playing with Bencic or Timea Bacsinszky at the Olympics.

"I will take my time and see how things will develop," she said.

Mirza could vie for gold in the mixed doubles with one of India's top men's players, Rohan Bopanna or Leander Paes, but she also hasn't thought about it yet.

"When we get to the Olympics, our focus will be that," she said, "but right now, it's definitely not."

There are other players very much in demand, such as Garbine Muguruza, considered a triple-medal contender for Spain. She's already decided to play singles and doubles with Carla Suarez Navarro and is now considering teaming with Rafael Nadal in the mixed. That is, if he's interested.

"Obviously the idea of playing with Rafa, so many people ask me," she said. "How can I say no? It's ridiculous."

Serena Williams also hasn't decided if she'll add the mixed doubles, which could mean a lot of matches in a compact nine-day schedule. Nonetheless, she floated some ideas in Melbourne for potential partners.

"I play well with John (Isner). I didn't get to play with Jack (Sock)," she said. "Anyone with a big serve, where I can just stand at the net and look good."

American Bethanie Mattek-Sands, meanwhile, is just hoping to make the cut.

In 2012, she won the mixed doubles title at the Australian Open and was ranked in the top 20 in women's doubles. When it came time to select the U.S. team for the London Olympics, however, she missed out on a spot — there were other Americans ranked above her, including the Williams sisters, who went on to win the gold.

Now, Mattek-Sands' chances are rosier. She's a two-time Grand Slam doubles champion and ranked No. 3 in the world in doubles.

"I've never played the Olympics, so it's kind of a lifetime achievement to go," she said. "I feel like it's out of my hands. ... I'm waiting for the call."

Max Mirnyi of Belarus must wait, as well, to see if Victoria Azarenka is interested in teaming up again to defend the mixed doubles gold they won in London, the first time since 1924 the event was held.

"If there's opportunity to defend the title, I would love that," he said. "But I would understand if she would be focused on singles only."

Regardless, Mirnyi may have a shot to make the men's doubles field, allowing him to play in a fifth Olympics. Two of his Belarussian compatriots are ranked in the top 100, Aliaksandr Bury and Sergey Betov.

His partner at the Australian Open, Filipino doubles specialist Treat Huey, however, probably won't be as lucky. He's currently ranked No. 34, but there aren't any other Filipinos in the top 200, making it incredibly difficult for him to make the field.

"We have a couple younger guys that are moving up the rankings," Huey said. "Hopefully, tennis grows bigger and bigger (in the Philippines) over the next couple years and four years from now, I'll have somebody to play with."