Milan's revolution continued with a 6-0 rout of Macedonian visitors Shkendija in the first leg of their Europa League play-off tie on Thursday.
It has been a busy off-season for Milan, who have overhauled their squad with the signings of Leonardo Bonucci, Lucas Biglia, Andrea Silva, Hakan Calhanoglu, Ricardo Rodriguez, Mateo Musacchio, Andrea Conti, Franck Kessie and Fabio Borini.
Montella is pleased with where Milan are at heading into Sunday's trip to Crotone as they look to dethrone Italian champions Juventus.
"I'm not kidding myself that the hard work is done, because this is practically a whole new squad, but the lads are working hard and I am happy," Montella said.
"There are players who need to integrate and let's not forget Serie A is more tactical and therefore more difficult than many other leagues. It'll be a real battle against Crotone on Sunday.
"I am very happy with the way this team is developing. We are only at the beginning, but it's a promising start. It's also gratifying to see the visceral enthusiasm of the fans in the stadium. It gives us an extra boost.
"Naturally the game immediately got on the right track and was perhaps better than we expected, so we had some dips in concentration that we ought to avoid in future. In general, it was a very positive evening. We won't take the second leg for granted, as every game is an opportunity to improve.
"The only negative of the evening was Jack Bonaventura's injury, but we hope it's nothing serious. He had a twinge in his thigh."