Five of Borussia Dortmund's imported stars have been put on detention by no-nonsense coach Matthias Sammer for returning from holidays unfit.

"Rules have been ignored," a furious Sammer, whose superbly drilled outfit took the Bundesliga title last season and lost the UEFA Cup final to Feyenoord, told Kicker magazine.

The German league's youngest coach punished the "flab five" last Sunday, ordering two Brazilians, Ewerthon and Marcio Amoroso, two Africans, Otto Addo and Sunday Oliseh, plus Czech midfielder Thomas Rosicky to sweat out an extra training session while the rest of the squad rested.

"To have a six weeks holiday is something very positive but that does not mean one should not do any training at all," Sammer said.

"Many players still have to learn to deal with success."

Earlier last week, Sammer took Amoroso to task after he failed to attend the club's first pre-season training session.

"If a player does not show up it proves that he has no respect for his team-mates," said Sammer, who has been in conflict with his Brazilian contingent, which also includes Evanilson and Dede.

The Latin American quartet were incensed when Sammer refused to give them an extra day off so that they could watch the World Cup final, in which Brazil beat Germany 2-0.

Dede told the Bild newspaper: "We have been angry with Sammer. I cried."