The Sardinians have taken maximum points in the first two weeks of the campaign and will look for a third straight victory at Palermo on Tuesday night.
"First place? Our thoughts should only be on avoiding the drop this campaign," Cellino said.
"We cannot start dreaming of something that is well beyond our limits.
"We just have to keep our feet on the ground and continue to work hard."
Cellino did warn his side must show a vast improvement with respect to their second-half performance in last weekend's 2-1 win over Novara, if they are to surprise Palermo at La Favorita.
"If in Palermo we play as we did in the second half against Novara, we risk conceding six goals," Cellino said.
Rivals Palermo, who beat Inter Milan 4-3 in their Serie A opener, will be desperate to bounce back from Sunday's 1-0 defeat at Atalanta.
"Everyone expected an easy win in Bergamo and we lost," Palermo coach Devis Mangia said. "I have a yong team and it's very easy for them to get over-confident after the triumph against Inter.
"The defeat in Bergamo should be a lesson that we cannot take any team lightly."
The hosts will be without midfielder Edgar Alvarez, who sustained a muscular injury at Atalanta.
Fabrizio Miccoli will partner Abel Hernandez in Palermo's attack.
Cagliari coach Massimo Ficcadenti will have all of his players available, with the exception of injured striker Moestafa El Kabir.