Radamel Falcao spearheaded the Spanish side's win with a stunning display in what was Chelsea's last match before the international break.
Blues' defender Bertrand says the team has overcome the hangover of that embarrassing defeat and are ready to put the result behind them.
"I think it was just a one-off. We're not looking into it too deeply," he told the club's official website.
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"We're really disappointed that we couldn't top it off [the Champions League success] and go and win that cup as well, but it's important we just focus on the league now. We've been fantastic in that, with three wins out of three, so we just need to forget that bad result."The 23-year-old signed a new deal at Stamford Bridge and has been deployed in an advanced midfield role in front of Ashley Cole and Bertrand says he has learnt a lot from the 31-year-old's approach to the game.
"Ash has won everything there is to win, he's won the FA Cup more times than anyone else and he still has the same attitude towards his football every day in training," added Bertrand.
"The way he approaches games is full-on 100 per cent, and that's the one thing I always take from Ashley: to have the right attitude and approach games in the right way."Betrand will see Jose Bosingwa this weekend, another Champions League winning team-mate of his, albeit in the blue and white hoops of QPR.
He added: "Getting the chance to play against him will be strange with him on the other side. He's one of their players now so we want to get the better of him!"