There’s one simple reason for that. He has rarely had to.
For half a decade, Federer had his way with world tennis, rarely tested as he marched to a haul of 13 Grand Slam titles.
But over the last couple of years, things have changed. Federer’s dominance has subsided as Rafael Nadal usurped his position as world No.1. Suddenly, Federer looked vulnerable, and on several occasions was unable to raise his game when it was called for.
His mental mettle was questioned and many critics suggested that while the Swiss magician was an outstanding front-runner, he lacked the stomach for a scrap.
However, Federer went a long way towards quashing doubts about his intestinal fortitude on Monday, with his courageous fight back from two sets down against Tommy Haas.
Haas turned back the clock with some inspired play in the first two sets and it looked as if Federer could crumble into the Paris dirt.
Yet back he came, first by eking out a tense third set, then by powering through the fourth and fifth.
Could it be that Federer is finding mental reserves that he didn’t realize he possessed?
Certainly back in January it looked as if he was fragile when matches became close, highlighted by his Australian Open final defeat to Nadal.
There seems to be a new-found assurance in Federer this fortnight though, and his revival against Haas was surely spurred by the knowledge that he may never get a better chance to win the French Open.
Nadal’s shocking exit to Robin Soderling opened up a giant opportunity for him, one which he came close to throwing away.
But with that hurdle safely negotiated, surely Federer will not let this golden chance to complete his career Grand Slam fritter away. Will he?