Enduring tough times growing up in a war-torn nation has helped shape the competitive character of Serbian players, Novak Djokovic said.

The world No. 1 extended his winning streak to 25 matches with today's 6-4, 6-4, 6-4 victory over Australian wild card Thanasi Kokkinakis in the Roland Garros third round.

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Asked afterward why the Balkan region has produced so many successful tennis players, Djokovic said genetics play a part.

"Tennis was never a traditional sport in our country, and it just became popular and successful maybe 10 years ago," Djokovic said in his post-match press conference. "But in country, you had Croatia that has nurtured a tennis tradition and success for a long time. I think just the genes are very good for sport in general. I don't know if you have been to the ex-Yugoslavian region, people are pretty tall, strong and athletic. I think that definitely helps as a good base, physically good base for the sport."

Djokovic said the demands of life during war-time has infused players from the region with the desire and determination necessary for success in a solo sport.

"You have these psychological factors that have affected many generations, talking about the tough times in wars and so forth," Djokovic said. "People also live pretty low standard compared to the western European countries, and they have to fight for [improvement] each day. I think that's something that strengthens them mentally. And that's a little factor that a lot of athletes carry inside their heads and subconsciously they are great fighters and they appreciate everything life gives them. I think that's where you already have a strong base for success in sport."

Photo credit: Philippe Montigny/FFT