Federer Nadal

Tennis legend Boris Becker says Roger Federer is still capable of winning Grand Slam titles. The Swiss tennis ace has won 20 Grand Slam titles and is leading the charts for the most number of Grand Slams won in the Men's Singles division.

Rafael Nadal is behind him with 17 Grand Slam titles. On the third position, there is Novak Djokovic with 15 Grand Slam titles.

Becker was Novak Djokovic's former coach and says Nadal and Djokovic can overtake Federer for the number one sport. Becker admits nothing is sure until the trio continues to play tennis.

"Who says Roger's not going to win more than 20? Maybe he's going to win Wimbledon this year. I wouldn't rule out (Djokovic going past Federer in Grand Slams). Can he do it? Yeah, but so can Rafa. Rafa has 17," Becker said.

"There are big question marks. These three champions keep on winning and until they still play tennis, nothing is sure," he added.

Becker says he has a mixed emotion looking at Novak Djokovic's red hot form for various reasons.

"Tennis is fickle and sensitive. A lot of things have to be right in your personal and private life. For Novak, it is perfect at the moment. Therefore he is on his way (to match Federer's feats) and hopefully nothing happens in the meantime," said the German, who himself won six Majors.

Is Becker surprised by Djokovic's red hot form?

"Yes and no. Because he has a champion's mindset and that is something you never lose. He has his work ethic back, as well as his discipline, his desire and his love for the game, so, it was a question of time when he is going to win again," Becker said.

"When he is on, he is very very good. And he is still young enough, younger than Nadal (who is 32). There is an open window for him in the next two years to add to his trophy collection. When Federer won his 20th, nobody thought anyone could even come close. Now you have two guys (Djokovic and Nadal). Every Grand Slam is witnessing history," he added.