Borussia Dortmund coach Jurgen Klopp expects the 2012/13 season to be his side’s toughest yet.

Klopp has led the Westphalians to back-to-back Bundesliga titles while they completed a league and cup double last season, but he is aware his side is going to struggle to top those achievements.

“The problem is that it is easy to improve when things were going badly for you, but now the bar has been raised extremely high for me and my team,” he said.

“We have got to put everything we have done to one side and if we have something to show for it again at the end of the season, then that would be amazing.

“We have done it twice and there can be no probability or guarantee about succeeding for a third time.”

Nevertheless, Klopp is not admitting defeat before the season starts, saying his side will accept the challenge of being the team everybody wants to beat.

“I place a lot of emphasis on motivation and enthusiasm,” he added in the Bild newspaper.

“I can transmit that to the team and if there were somebody here who I could no longer motivate, then he would not be so happy here.”

Klopp has done a good job motivating his side in recent seasons, but he does not feel he has reached his zenith yet.

“To become a truly great coach, I would still have to achieve a lot of other things,” he said.

“That also means the duration of success.”