The pair worked together at Pescara and Donatelli has no doubts the midfielder can handle the move to London.
"His technique, his determination and his tactical intelligence always impressed me," the Italian told Sky Sports. "He has always been strong in understanding those defensive tactical aspects and he is very mature tactically in terms of how he reads the game.
"He can cope with the gaps that emerge in midfield with great intelligence and he covers very well. He is the one who corrects the spaces and cuts out the passes between the lines in the defensive phase.
"After Sergio Busquets, he is tactically the strongest midfielder in Europe."