Blanco caught his spikes making a pivot in Saturday's game against the Chicago White Sox. He was given an MRI on Saturday.
Blanco's chances of winning a backup role on the bench will be impacted by the injury. Cubs manager Lou Piniella is on record as saying that he is going to try second baseman Mike Fontenot as a backup shortstop during some spring training games. It is unknown whether the Cubs will look for a trade to bring in another middle infielder this spring.
Piniella has been on record all spring saying that 19-year-old shortstop Starlin Castro will start the season at Triple-A Iowa. However, Castro will continue to get a lot of playing time during the exhibition schedule.
Blanco, 25, batted .252 in 53 games with the Cubs last season.
Bruce Levine covers baseball for ESPNChicago.com.