Chelsea goalkeeper believes that the red card shown to Nemanja Matic during Chelsea's 1-1 draw against Burnley turned the game in the opposition's favour.
The 26-year-old saw red in the 70th minute of the game, a decision which saw Sean Dyche's men increase the pressure in the dying minutes of the game.
And they were rewarded for their efforts when Ben Mee restored parity in the 81st minute at Stamford Bridge.
"We can understand the reaction if you saw how his [Matic's] leg bent in the tackle," Courtois told the club's official website.
"It is an emotional reaction when you know somebody could break your leg,
"In your head everything can happen and I don't think Nemanja did something bad but it was a push and the referee gave him a red card.
"Of course [the episode changed the match].
"It was already not an easy game for us when 11 against 11. You know with 10 players it will be harder because you cannot press up front and they will put long balls in.
"We took the lead, after that we had some problems but I think we had control but then the red card changed the game."
