Milan spent big to make sweeping changes to the squad in the off-season, but have lost the last three Serie A matches to sit 10th in the table.
With the recent string of poor results, Montella finds himself under mounting pressure, though he did receive the backing on Milan's CEO after the derby defeat.
"When things go wrong it's everyone's fault, we have to accept the criticism, even when it's exaggerated," he said.
"The club made choices for the here and now, but above all for the future.
"Everything is going to plan aside from a few defeats, which I take responsibility for, but if they hadn't happened we'd be talking about a balanced situation.
"I see a higher quality of play all the time, it takes time to do these things and that's proving to be the case.
"We have players who can and must grow, it's a good base to build from."