Pierce is on the 7-day injured list at Single-A Charleston due to an undisclosed injury.
He missed time earlier this season with a calf strain, per Ian Cundall of Baseball America, so it could be an aggravation of that injury. Pierce, the No. 14 overall pick in last year's draft, is hitting .252 with four home runs, six steals and a 28.6 percent strikeout rate in 34 games at Single-A.