Pirates Prospects is reporting (sub. req’d) that the Pirates have promoted their top prospect, right hander Mitch Keller, to Indianapolis. Keller has spent the season so far with Altoona, where he’s compiled a 9-2 record and 2.72 ERA. Keller’s season has been a bit uneven, as reflected in an xFIP of 3.67. He’s had some issues with the strike zone; his walk rate of 3.3 isn’t bad, but it was 2.3 last year. In his last five starts, though, he’s allowed just four earned runs, with his last outing being an eight-inning, one-hit affair.