The Phillies promoted Miller from Single-A Clearwater to High-A Jersey Shore on Monday, Jonathan Mayo of MLB.com reports.
Miller had been stuck in a 6-for-41 slump at the plate over his final 12 games at Clearwater, but he didn't compromise his plate discipline amid the dry spell, as he had still walked at a 20.4 percent clip. The 20-year-old was able to force his way to Jersey Shore after slashing .275/.401/.483 on the season at Clearwater while going 9-for-10 in stolen base attempts. He's regarded as one of the top lower-level prospects in the Phillies' system.