Napoli coach Rafa Benitez says his players should have been more clinical in front of goal against Dnipro Dnipropetrovsk.
Yevhen Seleznyov's only goal of the game means the Partenopei crash out of the Europa League and miss the opportunity to join Sevilla in the final.
And the Spaniard says it is vital to do well in their last three games of the season.
"We created a lot in the two legs but failed to take advantage," Benitez saidafter the game.
"We deserved more but the truth is that we wasted way too many goal-scoring opportunities. Tonight we could have scored with our first move so I'd say the key to the tie was that we had to score.
"We are upset and we cannot change what happened [in respect to incorrect referee decisions].
"At the end of the day they are in the final and we're bitterly disappointed for this.
"Our focus will now be shifted to the Serie A's last three games because we can still qualify for next season's Champions League.
"I'm optmistic ahead of the last part of the season."