Benitez felt Inter should've moved the ball around faster, but their game plan was ruined by the early penalty.
"I don't think we lacked character. The team tried and Milan took the lead so early on with that penalty, then committed a lot of fouls to keep us out," he said of the 1-0 derby defeat.
"It wasn't easy against a side playing with such intensity and focused on the counter. When they went down to 10 men, we perhaps lacked a bit of patience when choosing the final pass.
"We lost the ball too often in midfield and the team must learn to deal with possession better when behind.
"Milan had more control in the first half, but after the break we attacked continually. If we move the ball faster then we have more space, as we did in the second half down the left flank.
"We struggled to find that space for the through ball, mainly because Milan worked very hard to close them down.
"The penalty changed our game plan. We had intended to wait and create a bit of space behind their defence, but with Milan's early goal we had to push forward more and it was tricky."