The mistake completed a difficult week for the keeper, who was dropped by Zinedine Zidane in his first game back in charge of Real Madrid against Celta Vigo last Saturday, recalling Keylor Navas in his place.
Courtois has had a difficult debut campaign at Madrid since signing from Chelsea and feels he has been harshly treated in Spain for his role in the team's haphazard season, which has left them without a realistic chance of winning a trophy.
"I still consider myself one of the best in the world, even though the Spanish press want to kill me," Courtois told Belgian media.
"I feel strong, I'm calm, playing well and training well."
Courtois also shrugged off his mistake against Russia.
"I got a nudge from the Russian attacker," he said.
"I didn't have the strength to clear it. I made a bit of a mistake, but that's the life of a goalkeeper. After that, I calmed down and played my game."
Belgium forward Eden Hazard, who scored two goals against Russia after Courtois' mistake, tried to ease tension after the game by joking about his team mate's mishap.
"He watches a lot of videos of my actions and then he tries to copy me. The problem is he is much taller than me, so it isn't that easy," Hazard said.
(Reporting by Richard Martin; Editing by Christian Radnedge)
