According to the Monte Carlo Tournament director Rafael Nadal was the first player to register for the event boosting chances of his return at the event.
Nadal has been out of action since the Australian Open but there is hope he might return at the Monte Carlo Masters. He didn't confirm his participation but he did register for the event appearing as the first player on the entry list for the event. That is according to tournament director David Massey:
“Rafa was the first player to be registered. He really wants to play and is giving himself every chance to play.”
Obviously, none of this means anything in the grand scheme of things because Nadal still might withdraw before the event. He hasn't really spoken about his future with only people within his camp commenting on his return and simply stating that he will return when he feels ready.