Roger Federer, in three-set marathon, shows the heart of an Olympian

Does Roger Federer really need this?

At Friday's Olympic semifinal on Wibledon's Centre Court against Juan Martin del Potro, this was the score of his match: 3-6, 7-5 (5), 19-17. The time? Four hours, 26 minutes.   

"I don't think I have ever played as long a set in a best-of-three-set match," he said. 

We know professional athletes need to put on a good face for the Olympics or risk being called selfish. Just look back to how we viewed American professional basketball players in 2004. But 4 hours and 26 minutes? It some point in that third set, did it occur to him that he had done enough?

After all, he has already won a gold medal for Switzerland, though it was in 2008 in doubles. And adding another punishing tournament to a summer already packed with warmup events for the US Open might not be best way to keep himself fresh. 

But there is a reason that the press conference for Federer before the Olympics began was the biggest one for any individual athlete. (Yes, even bigger than the one for Michael Phelps.) His 17 grand-slam titles make him a sporting legend, like some other athletes. But who he is makes him revered as an ambassador of that sporting spirit so embodied by the Olympics.

He is, in short, sport's class act, and he proved it again Friday.

We all want our athletes to care about the Olympics – to play in them with as much passion as they would at the NBA Finals or the French Open. That is the hallmark of the Olympics, so half-hearted efforts stick out all the more conspicuously.

But for Federer, the Olympics are not a duty, it seems, but a passion. He calls his doubles gold in Beijing "the most incredible feeling I ever had on a tennis court." 

For someone who has had Federer's success, that is a shocking statement. More grand slam titles than any other man, seven Wimbledon championships, longer at No. 1 than any other man – and a doubles gold in Beijing is the "most incredible"?

Then you watch him outlast Juan Martin del Potro in the Olympics on a court that looks like it has been attacked by the sheep from the opening ceremony, and you understand. You see how he skipped the opening ceremony, just so he could be ready for his first-round match the next day, and you understand.

Like the weightlifter or the skeet shooter or the whitewater kayaker, Roger Federer just wants to win a gold medal for his country – desperately.

"The Olympics taught me a lot," he said at his pre-Olympics press conference. "Just seeing how other players practice."

By letting us all watch how he plays, he is repaying the favor.