(Reuters). The Belgium international keeper is yet to endear himself to Real supporters since joining last year and gave one of his shakiest displays against the unfancied Club Brugge, who took a 2-0 lead at halftime with scrappy strikes from Emmanuel Bonaventure.
Real's famously unforgiving fans made it clear who they blamed for the goals, loudly booing Courtois on two occasions before halftime.
Courtois was taken off immediately after the break, with coach Zinedine Zidane saying he was feeling ill, and his replacement Alphonse Areola kept real in the game with a crucial save against Bonaventure which brought loud applause.
Real eventually levelled the game thanks to goals from Sergio Ramos and Casemiro but were still left at the bottom of Group A with one point from two games, the 13-times winners' worst ever start to a Champions League group stage.
The Belgian was heavily scrutinised by the Spanish press, with newspaper AS claiming 'Courtois hits rock bottom'. Daily Marca focused on the booing he was subjected to, saying the keeper 'has a big problem with the Bernabeu'.
Zidane did his best to protect Courtois after the game.
"I'm not worried at all, we cannot blame Thibaut for the first half because we were all at fault, especially me," he told a news conference.
"If we had continued to play that way we would have lost the game, but luckily the players turned things around."
Courtois, who built his reputation as one of the game's top keepers during a three-year loan spell at local rivals Atletico Madrid, joined Real from Chelsea for a reported 40 million euros last year after a splendid World Cup campaign with Belgium.
He quickly overtook triple Champions League winner Keylor Navas as Real's number one choice but his first campaign coincided with one of the club's worst seasons in memory, which ended without a trophy.
Although Courtois has not made any memorable howlers, he has not yet produced any miraculous, game-changing saves which Navas was renowned for.
Navas' departure for Paris St Germain looked like a signal that Courtois had won the battle for the number one spot, but with the fans turning on him, he now looks set for another duel for the position, this time with Areola.