The 29-year-old has played in two cup finals for the Bluebirds, but he feels that keeping them in the top flight would better those accomplishments.
Whittingham told the club's official website: "It'd be huge. Probably the greatest achievement since I've been here. If we get three points on Sunday, we'll start to think about it.
"Sunday is probably one alongside the cup finals and play-offs I've been involved in; it's right up there with those sorts of games. It's always going to be when you know it's a game that you have to win.
"Everyone is raring to go. We all know what the job in hand is and what is required from us. It's now something we have to go and do. We can't wait for Sunday."
Cardiff are 18th in the Premier League with 30 points after 35 games this season.