Tennis feature: The four most notable rivalries and clashes in Roger Federer's tennis career

It is perhaps a mark of Federer's classy demeanour that no one had a bad thing to say about the 20-time Grand Slam champion. 

However, just because the tribute messages were full of lovely words does not necessarily mean that Federer went through his career without falling out with anyone. 

He did have his fair share of rivalries over the years – some more obvious than others. Here we look at four of Federer's most notable feuds and spats. 

Andy Roddick – Federer's most notable first rival on the court was Andy Roddick. The American was seen as the closest competitor to Federer at the time, although it is worth noting that their rivalry was pretty one-sided for the most part. 

The two would face off against each other on 24 occasions, with Federer leading the head-to-head 21-3. It is worth noting that Roddick was no slouch and possessed a serve that could trouble many an opponent. However, he couldn't bother the Swiss star too much when the two battled it out in the Grand Slam finals. 

Indeed, Roddick could argue that he would have won more Grand Slams than just the one he did claim if not for Federer. But Federer could say the same about his next big rival.

Rafael Nadal – The Spaniard proved the kryptonite to Federer's superman. When the FedEx express was running wild atop the ATP rankings, it was Rafa who brought the train to a screeching halt. And, in the process, showed not only how to beat Federer but also be more prolific than him. 

Nadal's dominance over Federer is most evident on clay, with Federer's sole French Open coming in 2009 when Nadal lost out in the fourth round to Robin Soderling. But Nadal would also do to Federer what Federer could not do to him – beat him on his preferred surface of the grass. 

Amazingly, despite the fierce rivalry, the two shared on the court, they were cordial and respectful. Nadal's retirement tribute to Federer, where he called him "my friend and rival", summed up their relationship best. A more classy rivalry has never arguably been seen in the sport. 

Novak Djokovic – Whereas Nadal and Federer shared similar values off-court, hence the mutual respect, the same could not be said about Federer and the equation he shared with the other member of the 'Big 3' in Djokovic. 

The Serbian frequently got on the wrong side of Federer, primarily due to on-court antics that drove many other tennis players mad too. Their on-court rivalry was mainly in favour of Djokovic, thanks partly due to his rise when Federer was steadily declining, but they were never the best of friends – and it showed every time they played each other. 

Stan Wawrinka – The strangest feud on the list is between Federer and Wawrinka. The two won Olympic gold medals for Switzerland but fell apart publicly during the 2015 ATP Finals. 

Wawrinka told the chair umpire that Federer's wife Mirka heckled him during a match the two played at the year-ending tournament. What's more, the two had a heated exchange after the game in the locker room. 

The two did patch things up eventually and became friends again, which isn't a surprise given the men involved.