MOSCOW, Russia - They've both taken their time and their chances, and now they're just two teams and the will to survive: Russians Maria Kirilenko and Nadia Petrova and Americans Raquel Kops-Jones and Abigail Spears will square off in one of the most important doubles matches of the year Saturday, the semifinals of Moscow - the survivor of which is headed to Istanbul.

For weeks now, the battle for the fourth and final spot in the doubles field at the TEB BNP Paribas WTA Championships - Istanbul 2012 has gone on. And Kirilenko and Petrova were quite a bit ahead coming out of the US Open - but Kops-Jones and Spears retaliated with some phenomenal results in Asia.

Having won three WTA doubles titles together in their entire careers beforehand, Kops-Jones and Spears matched that in Asia this year by winning three more WTA doubles titles together at Seoul, Tokyo and Osaka. They have gone 16-1 since the US Open, their latest win coming at the Kremlin Cup on Thursday against No.3 seeds Nuria Llagostera Vives and Sania Mirza, 75 64.

"We were all tired today, even our opponents, but we tried to have more energy and focused well today," Kops-Jones said of she and Spears' win. "It was a close match, but in the end I think our focus and energy made the difference."

Now Kops-Jones and Spears have set up a match-up - the showdown, really - with Kirilenko and Petrova. But while the stakes are high - the winner goes to Istanbul, the loser goes home - the Americans have everything in perspective.

"Qualifying for Istanbul is really exciting and important to us, but we're staying relaxed and trying to think it's just another match for us," Kops-Jones said. "This month has meant a lot to us, but we're really just playing to play.

"A run like this helps us in a lot of other ways too - it motivates us for the off-season and hopefully we can carry the momentum over to Australia."

The two teams have never played against each other.

"We just have to be positive," Kops-Jones said. "We have some little strategic things we'll try in the match, but mostly we just need to be confident we can beat them, and we'll try to just keep playing the way we've been playing."