Lazio made a bad start to 2012 with a 3-0 defeat at Siena, who picked up a much-needed win to take their coach Beppe Sannino out of the firing line.
Lazio had the chance to move into the top three with a win in the first Serie A fixture of the new year, but suffered a heavy defeat in which goalkeeper Albano Bizzarri was sent off.
Mattia Destro scored the opening goal and earned one of two penalties, which were both converted by Emanuele Calaio, as the home side wrapped up the win within the first 45 minutes.
Destro then had the final word 10 minutes from time with his second and Siena's fourth.
The 10 men of Lazio could not find any energy to recover in the second half and will now turn their attention to avoiding another painful upset when they face Serie B high-flyers Hellas Verona in the Coppa Italia on Tuesday.
Destro opened the scoring in the 11th minute after sliding his shot into the far corner, beyond the reach of Bizzarri.
Giuseppe Sculli had a rare chance for the visitors after half an hour, but he lifted the ball over the crossbar from six yards out.
The second Siena goal came from the penalty spot in the 35th minute when Franco Brienza's route to the ball was blocked by Marius Stankevicius and Calaio placed the ball into the right-hand corner.
He made it three on the stroke of half-time with Destro unfortunate not to be celebrating his second of the game instead.
He cut in between two Lazio defenders and chipped the ball past Bizzarri, who tripped him to the ground.
The ball struck the post and Destro managed to get back onto his feet to slot it into the unguarded goal, but the referee had already given the penalty and sent the Lazio goalkeeper off.
Calaio stepped up to the spot again, this time beating Juan Pablo Carrizo, who had come on for Lionel Scaloni.
A header wide from Miroslav Klose in the 49th minute was merely an illusion of a comeback as Siena soon took control of the game with Destro completing the comprehensive win in the 81st minute with a stooping header past Carrizo.
