A key factor in Federer's career resurgence past year was his controversial decision to skip the entire clay-court season.
'But he again decided not to play at this time of the season, as it will be on clay.
However, after a hip injury saw him skip Indian Wells and Miami, he needs to build up steam ahead of the French Open next month.
Red clay is the blood that runs through Nadal's veins.
The coach said: "He wants to play in everything, to always be available". "He says he will love to play against me again in best-of-five sets on clay", came the reply.
"I believe a tennis player of his quality depends less on that and more on being without physical issues".
Federer has enjoyed a renaissance by scaling back his schedule in the latter stages of his career, beating Nadal in a spectacular Australian Open final and in three other meetings on hard surfaces in 2017. Asked about Federer's decision not to contest a single clay-court event for the second straight season, Nadal grinned broadly. "He said that a couple of days ago - and I thought he would play Roland Garros". "Maybe a little contradictory".
Regardless of Federer's absence, Nadal will look to kickstart his season after an injury-prone 2018 so far.
Belgian star David Goffin was not so fortunate in a similar incident at the French Open previous year.
Rafael Nadal will return to competitive action for the first time since January this week.
'He says he will love to play against me again in best-of-five sets on clay, ' Nadal smiled.
Nadal, who made his comeback from injury during Spain's recent Davis Cup victory over Germany, is among a field which also includes Novak Djokovic of Serbia.
"I'm practicing well, I am playing with the right intensity I think", Nadal said during a media appointment, as per the Telegraph.
The Spaniard has a bye for the first round and will open his tour clay court campaign against either Slovenia's Aljaz Bedene or a qualifier.