Red Sox outfielder Rusney Castillo is expected to miss at least a week with a strained left oblique, manager John Farrell said Wednesday.

This is an unfortunate setback for Castillo, who is competing for the starting job in center field. Jackie Bradley and Mookie Betts will likely see most of the reps in center field with Castillo sidelined.

Castillo told CSNNE.com on Wednesday morning that his injury wasn't serious and he was expecting to be available for Thursday's spring game against Minnesota.

However, Castillo underwent an MRI, which revealed the oblique injury, after suffering the injury in his third at-bat during Tuesday's exhibition game against Boston College, per WEEI.com.