The Premier League champions are under pressure after losing 11 of their 23 games in all competitions this season, including the Community Shield defeat to Arsenal and loss to Stoke City on penalties in the League Cup.
Manager Jose Mourinho has brushed off speculation that he could be sacked if his team fail to progress and Courtois said everyone at the club needed to take collective responsibility for their poor performances.
"Who says we don't have the same commitment? Results don't say we aren't committed to the manager," the Belgian told the club's website (www.chelseafc.com).
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"Sometimes we have been better than other teams and still lost, that doesn't say anything about our commitment, results are just not there.
"We are still confident in the manager, we are one team and we are trying to get out of it with him.
"It's easy to say it's only the manager but every player, every member of the technical staff has to get better and then we will be near the top again. We have to keep working hard in training."
Courtois, who returned from a three-month injury layoff in Chelsea's 1-0 defeat by Bournemouth at the weekend, their eighth Premier League loss this season, says his team mates will play for the three points against Porto rather than just progression.
"If you play just to draw you never know what can happen in the last minute," he said.
"We will play to win. We want to give our fans a victory because this season we've lost too many games at home and it shouldn't be like that.
"All the players have to improve our level, we are a team but sometimes individually we haven't been at our best.
"You might have eight players at a top level and three a bit down but this season maybe it's been the other way around and it's more difficult, but we are still the same players from last season."
(Reporting by Simon Jennings in Bengaluru; editing by Sudipto Ganguly)
