UPDATE: The Dodgers have tweeted news of Ramirez's surgery and expect him to return in "approximately eight weeks."
An MRI revealed that "the ligament stabilizes the thumb was torn."
With Ramirez on the shelf until May, the Dodgers will likely move Luis Cruz over from third base to shortstop and put Juan Uribe, Nick Punto or Jerry Hairston at third base. After hitting just .228 in 2012, former top prospect Dee Gordon may get consideration to play shortstop in Ramirez' absence.
If Ramirez is out eight weeks, he will miss the first six games against the Giants. In 19 games against the Giants in 2012, Ramirez was 16 for 76 (.211) with two home runs and 14 RBI.