Francesco Lodi hit the early penalty which earned Catania a 1-0 victory against a Siena side whose problems go from bad to worse.
Siena coach Giuseppe Sannino had called for an immediate response from his players after their 4-1 defeat at Lecce on Sunday.
But, despite pouring pressure on the Catania goal in the closing 20 minutes, there was little sign of the message Sannino had wanted his players to send out.
They sit two points above the relegation zone, while Catania are now nine points clear of the bottom three, comfortably in mid-table in 10th position.
The game at the Artemio Franchi stadium was originally due to be played earlier this month, but was postponed due to heavy snow in Siena.
Siena had the first chance of the rearranged game, as Alessandro Gazzi's header was saved just beneath his crossbar by Juan Pablo Carrizo.
He then had to save well from Gazzi again, with a header destined for the bottom-right corner, then Gaetano D'Agostino - whose left-footed strike from outside the penalty area looked like finding the top right.
Catania had their lead after 23 minutes, with Gazzi handballing in the penalty area and Lodi driving a left-footed shot into the bottom right corner.
Carrizo denied D'Agostino again soon after the goal, as Siena probed for a levelling strike.
In terms of chances, the first 20 minutes of the second half belonged to Catania, with Adrian Ricchiuti driving one shot too high, goalkeeper Gianluca Pegolo getting down to save a low strike from Andrea Catellani which was heading for the bottom left corner, and Lodi threatening to sneak an effort from a tight angle inside the right post.
Then Siena reacted to their position and chances came at a flurry.
Gazzi set his aim on the top right corner but Carrizo pulled off another save, and then followed it by keeping out a shot from Claudio Terzi.
The goalkeeper continued to defy the home side, blocking a strike from Franco Brienza and then being thankful when a header from Erjon Bogdani and two shots from Pablo Andres Gonzalez missed the target in the closing minutes.
