Harry Redknapp's side blew the chance of a third straight win with a poor performance against Aston Villa a fortnight ago, a defeat which left them seven points adrift of safety.
And with just eight matches remaining, Jenas insists they must get the better of their west London rivals at Craven Cottage to keep the pressure on teams hovering above the relegation zone.
"If we're totally honest, we need to win on Monday night," Jenas said.
"A draw won't be a bad result because it keeps us moving forward and gets that momentum back up, but make no mistake, we need to be winning games. There are teams that can easily get sucked into it."
Jenas has netted twice in as many appearance since moving to Loftus Road from Tottenham in January, and Redknapp hopes his experience will prove crucial in the run-in.
Jenas added: "Harry knows the situations I've been in throughout my career and knows I can handle these types of battles. I've played in a lot of pressurised games throughout my career.
"I'd like to think that's why Harry brought me here - to play games, score goals and help the team out.
"The position we're in is tough, but the mood in the camp is positive. We're scoring goals, creating chances and there's a style about our play now that wasn't there a few weeks or months ago."