Palacio goal keeps Inter running
The pre-match buildup was centered on a training scuffle between Cassano and Inter manager Andrea Stramaccioni, and Cassano was left off the squad for the match in Sicily.
Cassano has had run-ins with authority figures throughout his career, from Fabio Capello at Roma and Real Madrid to former Sampdoria president Riccardo Garrone during his time with the Genoa-based club.
Having already lost another forward, Diego Milito, for the season with a knee injury, Cassano's absence weighed heavily.
Not surprisingly, Inter appeared distracted at the start and Gonzalo Bergessio put Catania ahead seven minutes in at the Massimino stadium after Inter defender Juan Jesus left him the ball deep inside the area.
Catania doubled its lead in the 19th following another defensive lapse with Giovanni Marchese left free to head in.
However, Inter organized itself in the second half, which began with goalkeeper Samir Handanovic thwarting two more Catania chances.
Ricky Alvarez scored for Inter in the 51st, heading in a cross from Rodrigo Palacio, and Palacio equalized in the 70th, heading in a cross from Alvara Perreira.
Palacio then scored the winner in the second minute of added time after getting set up by Esteban Cambiasso inside the area.
Inter moved into a tie for fourth with Lazio, 12 points behind Serie A leader Juventus.
Fiorentina is next in sixth after beating visiting Chievo Verona 2-1 with a 78th-minute strike from newly signed Argentine forward Marcelo Larrondo.
Manuel Pasqual had put Fiorentina ahead in the fourth, Ghana midfielder Isaac Cofie equalized for Chievo in the 38th and Larrondo decided the match with a close-range header, reacting quickly to redirect another header from Luca Toni.
Elsewhere, Udinese won 1-0 at Pescara with Antonio Di Natale scoring his 15th of the season; and Sampdoria beat visiting Parma 1-0 with a 58th-minute goal from Mauro Icardi, the 20-year-old Argentine forward who has scored eight goals since January;
Also, Bologna beat Cagliari 3-0 with goals from Saphir Taider, Alessandro Diamanti and Cristian Pasquato; and Giacomo Bonaventura scored twice as Atalanta won 2-0 at Siena, which remained tied for last with Pescara and Palermo.