The Azzurri are 11 points behind Serie A leaders Juventus with just six games remaining but automatic entry to the Champions League group stages would be a welcome consolation prize at the San Paolo.
AC Milan, however, are threatening to snatch second place and only a Goran Pandev equaliser at the San Siro last weekend kept the Rossoneri at arm's length.
Cagliari dispatched Inter Milan last week to reach 42 points and end talk of relegation but Cannavaro knows the Sardinians will not settle for mid-table obscurity.
He told sscnapoli.it: "We know they will be a difficult obstacle, for various reasons.
"Cagliari are safe and pressure-free but more importantly they are a team that plays good, organised football and has great ideas.
"We are fired up and focused because we know we will have to give our all. They are an opponent to be reckoned with because they have had a solid backbone for years."
The destination of the Scudetto is out of Napoli's hands with Juventus needing just seven points from their last six games to defend their title.
Second place is Napoli's to lose, however.
"We picked up an important point in Milan," Cannavaro added. "We realised we could have won the game and we did try to.
"We are satisfied with the performance and we have to carry on like that because it's up to us to secure Champions League football.
"There are six games remaining and we have keep pushing right to the end, knowing that we have to keep our four-point cushion over third place to be comfortable."
Napoli have no injury or suspension concerns but Cagliari are without the suspended duo of midfielder Daniele Conti and striker Mauricio Pinilla, with defender Francesco Pisano and midfielder Andrea Cossu missing through injury.
Head coach Ivo Pulga reflected on the run of results that has seen the Rossoblu take 26 points from 13 games to reach 10th place.
He said: "At the halfway stage of the season we only had 16 points and were in the relegation zone but then we changed tack and deserve our current position.
"Now there are six games left and we hope we can finish even higher."