The Swiss tactician believes that defeat in Istanbul effectively cost his team the chance of a semi-final berth, but urged his players to pick themselves up as they battle to qualify for the Champions League.
"The first leg compromised our qualification," Football Italia quotes Petkovic as saying. "I am sure we could've gone through otherwise.
"I am in any case very happy with the performance and compliment my lads, as we tried to win all the way to the end, even if it no longer counted.
"Perhaps we just lacked a little bit of luck. Now we will rest for a day, then prepare for Juventus on Monday night, as I believe Lazio can still finish in the top three."
Lazio are currently fifth in Serie A, seven points adrift of third-placed AC Milan.