Roger Federer insists that it was his back, and not his wife's heated conversation with Stanislas Wawrinka at last week's ATP World Tour Finals in London, that has him bent out of shape as he tries to prepare for the Davis Cup final for Switzerland against France starting Friday.

Federer said he was unable to practice Monday for this weekend's contests, after having tweaked muscles in his back in his three-set victory in the semifinal of the season-ending ATP event in London.

Roger Federer "not so cool" with coming within a game of defeating Andy Murray 6-0, 6-0

"It's definitely not good enough to practice yesterday," Federer said at a team press conference in Lille, France, where the tie will be played, according to tennis.com. "I feel it's definitely a little bit better than it was on Saturday night and Sunday and also Monday."

Federer said he has to be cautious with the injury that hurt his playing ability during the 2013 season, in which he dropped to No. 8 in the world. He will attempt to practice today in hopes of having the back loosened up enough for a couple more matches in the Davis Cup.

Andy Murray-Amelie Mauresmo partnership In Jeopardy

Multiple media outlets reported that Wawrinka exchanged heated comments with Mirka Federer, Roger's wife, during the third set in the semifinals.

According to tennis.com, Wawrinka was unhappy with the timing of the cheers by Mirka in the third set of their match. The Telegraph reported that "Mirka is understood to have challenged Wawrinka directly, accusing him of whingeing (complaining in an annoying way)."

Several media reports indicated that Federer and Wawrinka attempted to iron out their differences after the match. ESPN analyst John McEnroe said "Something went on in the locker room; there was a long talk between the players that extended well into the night. And the stress of that-I can't confirm all of this-but... I don't think that helped."

Both players said all the right things at the team's news conference Tuesday for the Davis Cup finals against France.

"I said, there's no hard feelings whatsoever. We're having a good time here. We are friends, not enemies," said Federer, according to tennis.com.

"We had no problem together. We talk about that already straight after the match. Not only about that, about many things," agreed Wawrinka.

But it's Federer's back that has drawn the most attention.

"I spoke to him," said Novak Djokovic, who won the ATP World Tour Finals and played an exhibition against Andy Murray instead of the scheduled final against an ailing Federer, according to another tennis.com story. "It's a question mark for Davis Cup as well."

Do you think a rift exists between Roger Federer and Stan Wawrinka? Comment below or tell us @SportsWN.