KEY BISCAYNE, Fla. -- Seeing Roger Federer look uncomfortable on a tennis court at this point in his career is a bit like seeing Niagara Falls run dry for a few hours. It's a wonder of the sporting world with the wonder temporarily siphoned out of it.
The brilliant statistics Federer has put up over the last three seasons were supplanted, on this afternoon, by some unaccustomed numbers: a whopping 51 unforced errors versus 15 for his opponent, Guillermo Canas of Argentina; a mere 25 percent of break points converted; a bizarrely lopsided 58 winners to Canas' 19. All of it added up a sum greater than its parts -- two defeats to the same player in the same month.
Federer did grumble a bit, further confirming the fact that he is mortal. "The statistics guys have no clue what an unforced error is," he said.
The world No. 1 said he considered the play of both men high-level, and was simply disappointed to lose. This match also was played at a high decibel level, as the indomitable Argentinian fans -- joined for once by their bitter soccer rivals, the dancing Brazilians -- turned Stadium Court into a raucous Davis Cup venue, waving flags at their outnumbered Swiss counterparts.
"As long as they don't boo the Swiss guys," Federer said, slouching in his chair in the interview room.
Yet the uneasiness Federer seemed to manifest at times Tuesday during his fourth-round loss to the 29-year-old Canas is nothing compared to the uneasiness tennis fans might be expected to feel. They're now in a predicament fans in cycling and Olympic sports know only too well -- trying to sort through what it means when an athlete returns from a doping suspension and starts winning.
Scottish cyclist David Millar is pulling that off in the European peloton at the moment, but he's had a good amount of public sympathy from the moment news of his case broke.
Millar, a former world champion in the time trial event, confessed to using the banned blood booster EPO before he was even formally charged. French police found used drug paraphernalia in a raid of his home, and he said guilt prompted him to keep the incriminating evidence as a reminder never to cheat again.
Whether or not Millar told the whole truth, he served his suspension and then returned to racing declaring himself a guinea pig -- someone who would see if it were possible to win clean. Canas denied cheating and has fought his case from the get-go, as he has every right to.
In February 2005 at a tournament in Mexico, Canas, then ranked 12th, tested positive for a diuretic banned by international sports authorities because it can be used to mask other performance-enhancing drugs. (He was No. 8 in June when the suspension was announced.) He claimed accidental ingestion, saying a tournament doctor had given him the wrong prescription.
But Canas lost in an arbitration hearing conducted under the auspices of the ATP and again in his appeal to the Court of Arbitration for Sport, because of the current rule that holds athletes to an absolute standard. If it's in your system, it doesn't matter how it got there.
The CAS panel did, however, reduce Canas' suspension from the maximum two years to 15 months. He forfeited some prize money and rankings points. Canas returned last fall and promptly began terrorizing the lower-level Challenger circuit in South America, winning four tournaments.
He entered this season ranked No. 142 and has risen to 55, winning another Challenger, an ATP event in Brazil, and a scintillating second round match against Federer at Indian Wells.
However, Canas is not done fighting on the legal front. He and his lawyers appealed the CAS verdict to the Swiss Federal Tribunal, which has jurisdiction because the CAS is located in that country. It's a step few athletes take because of fatigue, expense, and the fact that most of the time, their suspensions have already run their course.
Monday, the Swiss news agency ATS reported that the Federal Tribunal had taken the unheard-of step of voiding the already-served suspension and sending the case back to the CAS for further review. Canas' lawyer didn't want to discuss the details yet, but the player said he was "happy" with that development before English-language questions were cut off as the Spanish-speaking press closed in.
Welcome to the typical tortured legal saga and murky, unresolvable nature of modern-day doping cases.
Canas seems notably unintimidated by Federer. But neither player would speculate on whether Canas' absence from the tour, which coincides with much of Federer's recent, absolute dominance, might mean Canas doesn't have to battle as much mystique on the other side of the net.
"Really, I'm surprised because I beat two times the No. 1 in the world," Canas said. "I don't know what is my secret."
Before the Federer-Canas match, relaxed quarterfinalist Andy Roddick talked about the greater diversity in his game and unwittingly forecast the tipping point in Federer's loss.
"You're getting [this] influx of players who are playing with their legs a lot more," Roddick said. "They're running balls down … everybody was predicting tennis to go this way, left, and it went extremely right. That shows how much any of us know."
Roddick was referring to the dire predictions that tennis would turn into a nuclear serving exchange, with his own arsenal helping to foster that perception.
"It forces you to adjust," he said. "I can't play the way I played in '01 or '02 because a lot of guys are running those balls down now. I kind of have learned on the job and midway through my career to switch things up a little bit. It's an intriguing process."
Of Canas, Roddick said simply, "The guy didn't drop out because he didn't know how to play tennis."
"I think you expect that you don't really see him sitting around getting out of shape in that time off," Roddick added. "Maybe I'm a little surprised how quickly it's happened, but I'm not really surprised that he's come back and is playing well again. I mean, the guy competes and doesn't really give away much. The question never really was about his tennis. He could always play."
Tuesday, Canas beat Federer with his tireless legs, giving himself a chance on virtually every shot. Federer must have felt like he was playing a ball machine during some of their rallies. Whether Canas will ever be able to outrun the long, grasping shadow of his recent past is a different matter.
Bonnie DeSimone is a freelancer who contributes frequently to ESPN.com.