"Roger Federer seriously believes in his comeback, maybe he won't win another Grand Slam, but he can always get to the QF or SF" - Tommy Haas

Former World No. 2 Tommy Haas believes Roger Federer still has a lot left in the tank and can fight for the big titles once he returns to action.

Federer has not played a competitive match since Wimbledon last year. He aggravated a knee issue during the grasscourt season and underwent surgery following his quarterfinal exit at the All England Club.

The Swiss recently confirmed his presence at the Laver Cup in September and Basel in October.

During an interview with Bild, Tommy Haas said the 20-time Grand Slam champion would not attempt a comeback unless he believed he could still play at a high level.

"Roger seriously believes in his comeback and fights hard for it. He wants to know it again and not just deliver a PR appearance. I would never write Roger off. Maybe he won't necessarily win another Grand Slam. But he can always get to the quarter-finals or semi-finals – if he's healthy," Haas declared.

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Roger Federer's head-to-head record against Tommy Haas

Roger Federer hits a return to Tommy Haas of Germany during the BNP Paribas Open at Indian Wells

Roger Federer and Tommy Haas have been friends for a long time, but they have also competed against each other on a number of occasions. The duo have played each other 17 times, with Federer leading the head-to-head 13-4.

Haas won their first meeting at the Sydney Olympics back in 2000, as well as their most recent encounter in Stuttgart five years ago.

Between the 2002 Paris Masters and 2014 Indian Wells, Federer and Haas met each other 15 times, with the Swiss winning on 13 occasions. The pair have locked horns with each other in Grand Slams on five occasions -- twice each at Wimbledon and the Australian Open, and once at Roland Garros. Three of the five meetings went the distance and Federer won four of them with one walkover.

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