Frosinone president Maurizio Stirpe admits coach Fabio Grosso resigned via text message.
Grosso guided Frosinone to Serie A promotion last season.
However, he is now set to take charge of relegated Sampdoria.'
Stirpe said: I had asked everyone to let me know their intentions. The coach did not respond by June 9, but on June 14 he sent me a text message in which he went back over the great experience we had together, but said he did not feel like continuing.
He did not give me the reasons, nor did I want to know them. We must only remember the positive things from this rapport and his ability to transform a group of good players into a winning team.
Grosso achieved something that nobody in the history of this club had been able to do."