First, latest injury bout coupled with advanced age injects higher probability.
Second, there is a precedent. In 2016, Nadal had to withdraw after just the second round. That's just two years ago.
|Roland Garros Paris, France 2016.05.23 - 2016.06.05||
|Round of 32||56||L||(W/O)|
|Round of 64||99||W||63 60 63|
|Round of 128||100||W||61 61 61|
Add to it the fact that Nadal has competed - 'successfully' - @ EVERY Roland Garros since 2005. That's 12 freaking years.
Translation: 2016 was a MASSIVE aberration.
Bottom line: If he competes @ EVERY clay tournament this year - and wins (reaches final?) - 2016 could happen again - even before the second round.
Federer should keep his option open by leaving the door ajar to save face and nose - second asterisk @ FO notwithstanding.