If there has been one consistent criticism of today's golden era of tennis, it's that the top men's players are too nice.
But Tuesday at the ATP World Tour Finals, there was a hint of bad-boy blood after Roger Federer beat Novak Djokovic in a hasty, straight-sets win.
"Credit to Roger for mixing up the pace, giving me always a different ball," Djokovic told reporters. "He used the slice and spin very wisely. He served very efficiently. I made a lot of, lot of unforced errors. Just handed him the win, especially in the second set."
When told of Djokovic's postmatch remarks, Federer, who played remarkably well, took exception.
"Well, he wasn't as good as in the first set," Federer said. "But I feel, honestly, with the way he's played this season, you still have to put him away. It's not an easy thing to do. It's not like he played terrible. I know he can play better.
"Why did he play that way? I'd like to give myself credit for that, quite honestly, yeah."
Despite the overall amiable relationship between Djokovic and Federer, there have been reports of tension.
In his autobiography, "Wimbledon: My Life and Career at the All England Club" released earlier this year, Boris Becker, Djokovic's coach, said on the surface everything seems copacetic between the two, but that's not necessarily the case.
"[Federer and Djokovic] don't particularly like each other," Becker wrote. "The reason Roger is one of the highest-paid athletes of all time is because he's liked by everybody. But think about this -- you can't possibly be liked by everybody ... He makes good money out of his image, but would he make less if we saw a bit more of his true feelings?"
There were also some hard feelings during the 2011 US Open semifinals, when Federer took a dig at Djokovic after he blistered a slap-forehand winner to save match point. Federer told the press afterward that he never grew up "playing that way" and he believes in hard work -- not "lucky" shots.
Federer and Djokovic could meet again in the World Tour Finals if they both advance to the championship match.