The Baggies face relegation rivals West Ham United in a crucial game for both teams.
Appleton urged the fans to get behind him, saying: "Everybody knows that the three points are crucial. It would set up whoever wins for the closing stages of the season.
"With it being a home game, I want to get the place rocking on Saturday, and the more fans we have concentrating on positive issues rather than negative ones, the better."
Appleton is not planning to make wholesale changes and is confident the players will have recovered from the loss of Di Matteo.
He added: "We've had the players in today and they've responded really well. I will bring my own little stamp onto it. There'll be little subtle changes but Rome wasn't built in a day and I don't want to rebuild it over four or five days."