Tesser's team lie bottom of the standings, having managed just one win in their last 16 matches.
"Things are not going well for us but the team has the quality to get out of this situation," Tesser said.
"I spoke to the team after last weekend's 3-0 defeat to AC Milan. "Unfortunately, this is a period in which we are not able to win.
"I urged the players to find the maximum focus and determination for our next game.
"The players need to be more aggressive and eager to win.
"I have received a positive response from them and everyone believes that this team can defend its Serie A status by season's end.
"The game on Sunday is very important and we cannot fail."
Tesser has reason to be concerned as last weekend's loss - their third consecutive in the league - left his side seven points adrift of safety.
Novara have mustered 12 points in 19 games and have the worst defensive record in the competition with 38 goals conceded.
The promoted outfit can expect a tough test in Sicily with Palermo aiming to continue the momentum from their 5-3 triumph over Genoa last time out.
The result halted a six-match winless run in Serie A and handed coach Bortolo Mutti his first victory since taking over the reins of the team last month.
"I am happy with the victory," Mutti said. "Now we must give continuity to this result.
"We need to work hard and improve as we are conceding too many goals lately."
Palermo have given away eight goals in their last three league games.
They lie eighth in the standings ahead of this weekend's game at La Favorita.
Novara will be without defender Carlo Ludi, who underwent surgery on his left ankle and will be sidelined for six weeks.