Napoli lost 3-0 on Thursday night.
"The Europa League is not considered on a par with the Champions League, even if the clubs are of a high level," he said in his Press conference.
"I had told my players not to feel the pressure to score at all costs, but at times they cannot stay concentrated or isolate themselves from everything else. It felt like a friendly at one point and the San Paolo was half-empty.
"It is evident that a Coach, after a performance like the one we saw on Thursday, expects a totally different level in the next game.
"The result is relative, but the important thing is to see a team that is hungry, that attacks the opponent and fights for every ball. We usually do achieve this, but it didn't happen in the last match.
"It may seem like I am making tactical changes, but these are the same mechanisms and movements that we have always used. It is my fault we failed the last two games, because the team did not have the right approach."