Inter was beaten 5-0 by PSG in Munich, so that the club was brought to the ground after also blowing the Serie A title and being beaten in the semi-final of the Coppa Italia.
Sommer said Bild: “Lately we have missed something at the important moments.
“Both Saturday, but also in the competition, where we have dropped many points. That is football.
“Everything can radically change in the space of two or three weeks. We have been punished hard for our mistakes this year.
“That hurts us.”