The injury occurred on Saturday, and after an MRI, GM John Mozeliak told reporters that initial results were "not positive." Early results indicate a possible torn ligament in Peralta's left thumb. The former All-Star left camp early on Monday to undergo further testing.
The 33-year-old hit .275 last season, with 17 home runs and 71 RBIs. The team has not yet looked for help at the position, and plan to wait on the results of further testing to decide whether or not help is needed.
The team added Jedd Gyorko in the off-season, and he was the guy starting at shortstop on Monday. Gyorko played 29 games at shortstop last season for the Padres, hitting 16 homers and driving in 57.
Peralta joined the Cardinals in 2014, and the former Cleveland Indian and Detroit Tiger is signed trough the 2017 season.