The top two in the table meet on Saturday in what is expected to be a sell-out at Loftus Road.
Warnock believes the Rangers defence will face their biggest test of the season against Cardiff, who boast new England international Jay Bothroyd and Michael Chopra in attack.
"The game has come in November and there are just too many left to say this is the vital match," Warnock told the Fulham & Hammersmith Chronicle.
"But I am thrilled it is a sell-out and our defence will know they have been in a game, although we have also got the resources to score goals."
Source: PA
Source: PA