I do not think that many people under-estimated Federer like they under-estimated Nadal. I remember that many people always saw Federer as the favorite and Nadal as the underdog but mostly Nadal emerged victorious of the two and many people used to see Nadal's victories and achievements as some sort of miracle when there is absolutely no miracle in that. According to me, Nadal is a physical freak which is the main reason why he was able to train so intensely hard and give maximum effort for each and every point over a period of 20 years. Other players including very successful ones like Federer and Djokovic simply do not have the ability to practice so intensely hard and give maximum effort for each and every point as they need to focus more on the energy conservation for the subsequent games, matches and tournaments and they are more prone to getting tired since they are more of ordinary human beings and are not physical freaks like Nadal who is gifted with an unlimited amount of energy by genetics. In my humble opinion, Nadal is the one who was/is the real favorite to win against anybody else and people are very sort sighted not to realize that fact. Even now, I won't be even one bit surprised or shocked even if Nadal goes on to win many more slams and big titles going forward and manage to surpass Djokovic's slam record and masters record. I honestly do not think that Djokovic's records can be considered safe from Nadal because Nadal is capable of achieving anything by sheer will power and extra ordinary ability to work continuously hard without getting tired and nature has gifted him with that ability. According to me the real miracle is Djokovic somehow leading the slam race over Nadal as of now which may change very quickly. This is my very honest and sincere feelings.