The English champions, who are 14th in the Premier League table after losing eight of their 15 games so far, then travel to take on surprise leaders Leicester City on Monday.
"Of course we are upset, but we have to regroup again and show strength against Porto in the Champions League and next Monday at Leicester," Courtois, who made his comeback on Saturday after missing 17 games through injury, told the club's website (www.chelseafc.com).
"It's an important week for us. On Wednesday we have to win to make sure we are first and qualified. That will be a big boost for the team as well.
"Then Leicester away is a difficult game. We knew last year it was not easy there and now they have the confidence and are playing really well. It will be a very tough game but we are confident we can push on there."
(Reporting by Shravanth Vijayakumar in Bengaluru; editing by Sudipto Ganguly)
