Following the Aquile's crushing loss at the hands of Napoli, the trainer has demanded more concentration in front of goal, starting against the Bianconeri on Sunday
The Aquile's positive start to the season was dented by successive defeats to Napoli and Genoa, and the trainer hopes his team can turn their fortunes around on Sunday.
"I am not worried about my team," the Bosnian manager said to reporters at a press conference. "We must continue not giving in, and react better to difficulties."
"Klose's disallowed goal [against Napoli] caused us to lose some intensity, but I did see the right fighting spirit in the opening half of the match.
"We have created chances well in our last three games, albeit without scoring. We therefore have to take our chances from our opportunities, and think about things with more optimism."
Star midfielder Hernanes is a fitness doubt for the match against Siena, and Petkovic admitted that his team will have a tough time without the Brazilian.
"We will access Hernanes' injury tomorrow, while Ederson is not fully ready physically. Siena, meanwhile, are in great condition.
"We just have to dominate possession and become more clinical, taking the chances that arrive during the game."