Lazio were shocked at the weekend, losing 3-0 to then-bottom side Siena, but Petkovic has said that his side will turn up in Rome with "much more" focus.
"I'm sure tomorrow we will see the real Lazio," Gazzetta dello Sport quotes Petkovic as saying.
"Borussia will not give up until the last minute. Matches against German teams are not over until the referee blows his whistle.
"It will take discipline on our part. We need to be much more focused and willing to prove this on the pitch."
Lazio have drawn each of their last three matches in the Europa League.