Rome, December 17 - Serie A's bottom side Siena appointed former Sampdoria boss Giuseppe Iachini as their head coach on Monday. The club sacked Serse Cosmi following Sunday's 4-1 drubbing at Tuscan rivals Fiorentina, their third consecutive defeat. Siena are bottom with 11 points from 17 games although they would be above the relegation zone if it were not for a six-point penalty they were given for their players' involvement in a betting-related match-fixing scandal. Iachini, who has also had stints with Chievo Verona and Brescia, has signed a contract that runs until June, with an option for his deal to be renewed if he keeps Siena in the top flight. Cosmi is the sixth coach to leave a Serie A club so far this season. Palermo, Chievo Verona, Cagliari, Genoa and Pescara have also changed coaches.