Inter Milan have moved nine points clear at the top of the Serie A table while Lazio secured a much-needed win.
Jose Mourinho's Inter look good for yet another title and Saturday's win over Siena has only enhanced their claims.
Lowly Siena did not go down without a fight and went in at the break level after Houssine Kharja cancelled out Maicon's 34th minute opener.
However, the visitors were not to be denied and Siena were unable to fight back a second time when Maicon bagged his second of the game on 83 minutes.
Lazio returned to winning ways in Serie A on Saturday following a 1-0 success over Palermo.
The Biancoceleste had gone five without a win domestically after brushing aside Siena in early November.
The game was ultimately decided shortly after the hour mark when substitute Tommaso Rocchi converted Mourad Meghni's cross.
Palermo's hopes of getting something from the contest ended when Federico Balzaretti collected his second yellow card of the match.
The win lifts Lazio two places into sixth in the Serie A table, while Palermo remain in ninth on 23 points from 17 outings.