Belgian goalkeeper spent three successful seasons at Atletico and returns to the club in the Uefa Champions League group stage on Wednesday.
Atletico Madrid v Chelsea: Courtois expects warm welcome but not for former Real Madrid striker Morata
Chelsea goalkeeper Thibaut Courtois has said he is expecting a good reception from Atletico Madrid fans but has warned teammate Alvaro Morata to expect the opposite.
Courtois spent three successful seasons on loan at Atletico from 2011, winning the Primera Liga title, Copa del Rey and Europa League, as well as reaching the 2014 Uefa Champions League final.
The Belgian goalkeeper returns to his former club on Wednesday as Chelsea look to cement their place at the top of their Champions League group following the 6-0 win against Qarabag in the opening round of matches. Atletico drew their opener against Roma in the Italian capital.
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However, while Courtois is set to get a warm welcome from the Atletico terraces, Morata, formerly of Atletico's arch rivals Real Madrid, could be in line for a hostile atmosphere.
"He will get a different one from me. Alvaro played a lot of games against Atletico. I think he scored, I am not sure, so for him it will be a big game against his rivals," Courtois told the Chelsea website.
"For me it will be more friendly but between the 90 minutes we are playing there will be rivalry for me as well because they want their team to win.
"We know he is a top striker. We know he has this ability and we're very happy for him that he scored his hat-trick (against Stoke City on Saturday) ... a striker lives on goals and he has already scored a few important ones this season."
Courtois, 25, also said he is looking forward to seeing Diego Costa, who recently left Chelsea to rejoin Atletico after falling out with manager Antonio Conte.
Costa will be eligible to play for Atletico from January 2 when the Spanish transfer window opens and the club's transfer ban ends. Fifa had banned the Madrid side for illegal transfer of minors.
"He is a very good friend and it will be nice to see him there," Courtois said. "I am happy that until the New Year we don't have to face him and I hope we continue in the Champions League."