Robinho was again left out of Milan's squad by coach Massimiliano Allegri who admitted on Saturday that the Brazilian striker was struggling to have any impact on the Serie A title-chasers.
"Robinho is not in a great moment, the other strikers are playing well so I prefer to let him rest," said Allegri.
The 28-year-old Robinho has only scored five times this season in 26 matches, a record which has frustrated the Milan coach who said the club does not need players who lack motivation.
Dutch veteran Clarence Seedorf has also angered Allegri although his absence from the squad which travelled to face Siena for Sunday's game was attributed to a calf injury.
Top scorer Zlatan Ibrahimovic, with 24 goals this season, will play Sunday alongside either Antonio Cassano or Stephan El-Shaarawy with Kevin-Prince Boateng in support, added the coach.
Milan are second in the table, three points behind Juventus, who face Novara on Sunday, with four matches left.