Milan were beaten in the first-leg of their round 16 playoff in Rotterdam.
Donati said on TMW Radio: “I think it's quite simple, you have to attack and defend all together. I can't think that the strong offensive players that Milan has can only think about the offensive phase. You have to do both phases, at today's pace everyone has to run.
"If you don't run, you lose balance and you get slammed. Leao or Joao Felix lose the ball, they have to come back strong. With teams that put so much intensity you get tired. Inter won a Champions League with Eto'o who was a full-back. If the team can support some players who don't come back then it's fine, but if the team can't support them then it becomes a problem. It's up to the coach to find the solution to best manage the offensive potential available."
Donati also said: "The coach lives with the players all day long, if yesterday he chose to play the game this way he will have made his assessments. It is a fact, however, that there was a lack of balance yesterday too, now it is up to him to find solutions.
"A solution must be found, perhaps he can choose to rotate the four offensive players without having them all play together. However, solidity is needed, in all this it must be added that yesterday he lost due to a goal conceded due to an injury to the goalkeeper."