Roger Federer’s last-minute pullout from the ATP World Tour Finals at the O2 Arena in London yesterday completely stunned a disappointed crowd which was anxiously awaiting a blockbuster final between the Swiss icon and Novak Djokovic. Federer, wearing a warmup suit courtside, stated he was unable to compete in the final due to a back problem suffered during his gruelling three-set win over Swiss compatriot Stanislas Wawrinka in their semifinal Saturday night. The announcement from Federer, a much beloved fan favorite, didn’t even generate so much as a smattering of boos from the crowd, which had paid good money for tickets to the final. Such is the esteem in which Federer is held. Strangely though, there was some mystery regarding the withdrawal. Federer didn’t show any signs of duress during his match with Wawrinka and didn’t indicate there was any problem with his back in the press conference about two hours afterwards. Rumors of a row between the two after the presser have surfaced. Federer’s wife Mirka is reportedly at the center of the flap. Wawrinka and Federer apparently argued late on Saturday night after allegations that Mirka heckled Wawrinka from the players’ box during the match. ESPN commentator John McEnroe suggested on air yesterday that the tension between the two Swiss could have exacerbated Federer’s back troubles. “Something went on in the locker room, there was a long talk between the players that extended late into the night,” McEnroe said. “And the stress of that, I can’t confirm all of this, but a lot of this went on and…I don’t think that helped the situation.” McEnroe contended the post-match dispute meant Federer did not get immediate treatment on his injured back, which led to him withdrawing from the final. At the very least, the confab caused anger and consternation. Wawrinka and Federer have always had a close relationship, though it must be said that Wawrinka was never a threat to Federer on the court until this year. It is known that Federer did not return to his hotel until well after midnight Saturday night. So whether it was truly the back or a sleep-deprived night triggered by the spat, Federer wouldn’t have been able to pry No. 1 away from Djokovic anyway. Still we all missed what portended to be a doozy of a final.