The 49-year-old claims sides such as the Biancocelesti and Juventus must be able to balance their European commitments, insisting they "must not fail" to beat Siena
The Biancoceleste played out a thrilling 3-3 draw with their Bundesliga counterparts in midweek - a match which Petkovic himself described as "crazy" - but the boss has insisted European competition is no excuse for poor domestic form.
“We have no alibis. Europe can cause tiredness, as we saw with Juventus losing to Roma last night, but we wanted the bicycle, so now let’s get pedalling,” Petkovic said at a press conference.
“We are close to the levels we were at a few weeks ago, so I am not worried. Are we thinking about the Scudetto? No, if anything we’re looking over our shoulder, seeing as from the start of the season people treat us as if we’re a little club.”
Lazio have traditionally struggled against Siena, and were beaten 4-0 in the fixture last season, but Petkovic has urged his side to push for all three points on Monday.
“We must not fail. This game will require us to play at 120 per cent of our potential. It’s true we have been a little unlucky recently, but fortune favours the brave," he went on.
“It just means we must be more concentrated and gritty, especially in defence. We can’t keep conceding goals on set pieces.”