Sascha Lewandowski was presented as the head coach of Bayer Leverkusen for the second time on Monday and demanded an immediate change in his players' mentality.
Lewandowski has been appointed as Leverkusen boss following the dismissal of Sami Hyypia on Saturday.
Both had worked together after the sacking of Robin Dutt in 2011 before Hyypia took sole charge last summer, and Lewandowski returned to his previous role of youth team coach.
Now back in the hot seat without assistance, Lewandowski has vowed to halt Leverkusen's slide down the Bundesliga table.
“We don't have much time so the players are going to have to respond immediately,'' Lewandowski told a news conference. “We cannot just carry on with things the way they are. When I found out the club needed me, it was only natural I accepted.''
Leverkusen have won only one of their last nine matches, dropping to fifth at the weekend and seeing their hopes of qualifying for next season's Champions League suffer a setback.
“I've analysed the situation in depth the past two days to see which way we need to go," he said. "We've got to turn a few screws to ensure we make progress as quickly as possible.''
Lewandowski's first game in charge comes against Hertha Berlin at the weekend.
Leverkusen are behind fourth-placed Borussia Moenchengladbach on goal difference with five games of the season remaining.