Two second-half goals saw Siena defeat Inter Milan 2-0 at San Siro in Serie A on Sunday.
The Nerazzurri started the game brightly and created their first chance after just six minutes when Fredy Guarin took an attempt on goal from the edge of the penalty box.
However, the Colombian's effort sailed over the Siena crossbar.
Four minutes later Guarin had another chance to put Inter into the lead when Antonio Cassano released a pass for him, but he arrived too late at the back post to receive the ball.
Inter continued to dominate proceedings in the subsequent minutes, with Wesley Sneijder and Esteban Cambiasso testing Siena goalkeeper Gianluca Pegolo.
Andrea Stramaccioni's side commenced the second half lively too, as Cassano tested Pegolo with a deflected shot in the 48th minute and Diego Milito's header went narrowly wide eight minutes later.
The Milan giants had further chances, with Ricky Alvarez and Yuto Nagatomo taking aims at the visitors' goal.
Then much against the run of play in the 73rd minute Siena broke the deadlock through a Simone Vergassola goal.
Alessandro Rosina galloped down the right wing to pass the ball to Vergassola who, after playing a lovely one-two with Emanuele Calaio, fired home.
It could have become 2-0 to Siena in the 82nd minute had Handanovic not kept out Calaio's header.
Cassano went close again for Inter two minutes later, but it proved futile as Siena wrapped up the points in the second minute of injury time when Francesco Valiani headed home Alessio Sestu's cross.
