Ronaldinho is set to miss AC Milan's Serie A game with Siena on Wednesday after injuring his knee in Sunday's 1-0 win at Atalanta. "He had a bruise to his right kneecap. I think that even he will need a couple of days rest," Milan doctor Massimo Manara told the club's official site. French midfielder Mathieu Flamini will also be rested as Milan have Marek Jankulovski suspended. Milan have a chance of going top if they beat Siena, with one point separating the Rossoneri from top trio Udinese, Inter Milan and Napoli.