The Portugal centre-back has clearly being identified as the culprit for Chelsea recent defeat against Aston Villa which knocked them off top spot in the Premier League.
Ancelotti replaced Carvalho with Branislav Ivanovic and Juilano Belletti replaced the injured Jose Bosingwa at right back.
Chelsea went on to score four goals against a poor Athletico madrid side without letting in one past Petr Cech.
Carvalho was almost sold in the summer following last season's mixed fortune which consisted of a couple of injuries.
But the centre-back has been the number one choice this season to partner John Terry in the centre of the defence.
Ancelotti said; "I decided to rest Carvalho from the side."
Hmm well that's one bit of spin that won't wash with the hardcore Chelsea fans who worship the player and see him as the lynchpin of the defence.
Chelsea play Blackburn Rovers in the late kick-off on saturday and it will be intersting to see if the "rested" Carvalho is in the side.