Lazio have struggled for consistency this week.
"Can the Europa League give a rosier hue to this season? It's rosy anyway, as we achieved our first objective with qualification and now want to finish top. It can help us in future," said Petkovic.
"Recently I have been happy with the cohesion and style of the team, which we have rediscovered. If we analyse the recent games, we played well and simply did not get the result due to individual errors. There are few matches in which our opponents out-played us.
"Obviously when the results don't come it can affect your confidence, losing the belief we had last season when we felt that we could always resolve matters.
"I believe in this squad and these lads. I very rarely felt otherwise, as this group gives its all. We must, without too many proclamations or comments, show that on the field.
"These three points would be fundamental for the end of the year. We haven't won in 10 matches, but we have also lost only one of our last 19 European ties. Not many sides can boast that run."
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