The Nerazzurri are back on track in Serie A, but have now lost both their Europa League games to Hapoel Beer-Sheva and Sparta Prague, so sit bottom of the group.
“If you start with the wrong attitude, you can talk about tactics all you like, but the first thing is to have the right mentality.
“On the second goal we gifted an incredible opportunity. It's not possible to concede a goal like that," the coach told Sky Sport Italia.
“In the second half we did slightly better, but certainly not playing the way I want to see Inter play. After the red card it all became more difficult and the 3-1 sealed it.
“We gave the ball away too many times and must improve a great deal in that sense, because otherwise it's going to be difficult over the next few games too."