Pirates outfielder Daniel Nava underwent back surgery and is expected to be out for 10-12 weeks, Pirates director of sports medicine Tom Tomczyk said on Wednesday.

Nava signed a minor-league contract with the Pirates a week before the start of spring training, but participated only in the first day of full-squad workouts. Nava consulted with the Pirates' medical staff but sought out a second opinion from orthopedic surgeon Dr. Chris Yeung in Phoenix.

Yeung performed a microdiscectomy, a spinal surgery to repair a herniated disc, on Nava on Tuesday.