Matteo Destro earned Siena a shock last-gasp victory away to Atalanta, a crucial result for those teams trying to achieve mid-table security.
The Orobici needed just one more win to be mathematically sure of safety, while Robur were also seeking mid-table comfort. German Denis was back in the Atalanta squad after several weeks out with a sprained ankle, though Matteo Brighi, Guido Marilungo and Daniele Capelli remained on the treatment table. Siena missed Angelo, Emanuele Calaio and the suspended Franco Brienza.
Federico Peluso created the goal for Ezequiel Schelotto after nine minutes, whipping in a cross with the outside of his right boot for Schelotto at full stretch to volley in from seven yards.
However, Siena fought back and Andrea Consigli was penalised for bringing down Larrondo from six yards when mistiming his attempt to close down the striker. Larrondo got back up to take the penalty and side-footed it centrally past the diving goalkeeper.
Luca Cigarini charged down a Mattia Destro snapshot and Gianluca Pegolo flew to palm away a Simone Tiribocchi volley.
Schelotto also volleyed over from a deflected Peluso cross, while Guglielmo Stendardo went very close to a second for Atalanta when his header skimmed the woodwork.
Denis made his comeback for the final half-hour, but it was Siena who snatched a shock winner in stoppages.
Destro came out of nowhere to get the winner for Siena. He ran down the left side of the box and skipped past Stendardo to beat the goalkeeper with an angled drive from close range.
Both Coaches were sent off after a scuffle on the touchline during the goal celebrations.
See the latest Serie A predictions and betting tips with Eurotips.co.uk