Chelsea face German side Werder Bremen in the Champions League later Tuesday in a bid to begin a campaign which, last season, ended before the quarter-finals stage.

Since arriving from SV Hamburg last month, Boulahrouz has been stunned by a combination of cheeky antics and the efforts some teams make when playing against Jose Mourinho's expensively-assembled side.

"It's unbelievable how much venom surfaces when Chelsea are the opponents," Boulahroux told The Sun.

"Against Blackburn, not only were we kept up all night by hoax wake-up calls at the hotel, but on the pitch they used every means possible.

"The next game against Middlesbrough, they went at it intensively for 90 minutes and beat us.

"Then a week later at home against Portsmouth they (Middlesbrough) lose 4-0."