The Nerazzurri have not won in their past four Serie A matches and have now drawn 14 of their league fixtures this season.
"We let our concentration slip and conceded fortuitous goals but that sort of thing mustn't happen," he told the club's official website.
"You have to maintain your focus for 95 minutes. It's not all down to luck, we have to accept our own responsibility too. We can't go looking for excuses or alibis.
"Today we were finally given a penalty but we weren't able to make the most of it. That's they way it is, we just have to knuckle down and stay calm, stick together during the game and play with the determination we need to get a result."
Inter are currently fifth in the Serie A table.