Udinese were two goals in front after just five minutes but were held to a draw by Siena, who hit back with a pair of second-half strikes following Andrea Lazzari's red card.
Dusan Basta put the visitors ahead after three minutes with a powerful effort, with Antonio Di Natale doubling the lead soon after from close range.
But the game changed when Lazzari received a second caution after 52 minutes as first Emanuele Calaio (70) and then Ze Eduardo, with a 77th-minute penalty, scored for Siena.
The result leaves the hosts on minus four points following their six-point deduction at the start of the season.
Basta's opener came somewhat out of the blue, a strong effort into the top corner from the edge of the area.
He was involved again two minutes later as Udinese scored a second.
Basta this time found Di Natale with a well-directed long ball and the Italy international did the rest.
Siena were well off the pace and needed Gianluca Pegolo to make a smart save when Di Natale sent a superb volley towards goal.
Despite his side's dominance Udinese boss Francesco Guidolin was sent to the stands just before half-time for arguing with officials.
Seven minutes after the restart, Lazzari followed his manager, dismissed following a foul on Rosina.
That brought Siena back into the match and substitute Ze Eduardo struck the crossbar in the 65th minute.
Five minutes later the home side had their breakthrough, Calaio nodding in at the far post after a hanging cross from Alessio Sestu.
The momentum was firmly with Siena now and the second came when Maurizio Domizzi hauled down Angelo Ogbonna in the box.
Ze Eduardo slotted home the spot-kick to ensure a share of the points.