The Cubs made the moves before Thursday's game against Arizona. They promoted left-hander Zac Rosscup and right-hander Neil Ramirez from Triple-A Iowa and optioned righty Blake Parker to their top minor league team.
Ruggiano says he has a Grade 2 strain and says the best-case scenario is for a return in three to four weeks. He was injured in the ninth inning Wednesday trying to make a catch in right field.
Ruggiano is hitting .229 with one home run and six RBIs.
Rosscup made one previous appearance this season for the Cubs, pitching 1 2-3 scoreless innings during the second game of a doubleheader against the New York Yankees on April 16.