The Rhinos remain fourth in the Super League but after Wigan's defeat to Hull, third is still an option for the Rhinos going into next week's clash away to the Warriors.
After the match the Leeds boss singled out hard-working forward Jamie Peacock, who was outstanding in leading his side.
"I am pleased we won tonight. It was a tough game and we found a way to win," said McDermott. "Catalan gave it a real go and you could see that.
"I thought we deserved it. It was similar to the Hull KR defeat in the nature of the game, it was scrappy at times.
"I wouldn't pick out too many people for a mention, but it's hard to ignore the effort of Jamie Peacock.
"He has been tremendous this year. At this stage of the year people start banging the drum for Man of Steel and it would be hard to argue against him.
"We now have a chance for third place and we'll keep fighting. It puts us in good stead, this type of game, going forward into next week and the play-offs."
A late try by Danny McGuire on his return from a broken leg clinched the victory and McDermott said: "Danny hasn't played since the game at Hull. It's big to have him back, he has trained really hard.
"The next task is to try and get him as match-fit as possible in such a short period of time."
Catalan head coach Laurent Frayssinous admitted his disappointment with his side's execution during the tight contest, but he insisted his team remain a threat come play-off time.
"We didn't execute again. There was some improvement today, we want to play into space and there will always be errors. We can still improve in our execution," he admitted.
"Ian Henderson has got a twisted ankle and he will have to pass a test on Saturday. Julian Bosquet was strong tonight. It will be a big loss for us when we lose Remi Casty next year, so we will have to find some more leaders from within the group.
"I do believe we can do something in the play-offs. I believe we can perform against any team and tonight we showed that. We need to learn from tonight, in the play-offs we can't just play for 72 minutes."