Keller threw six shutout innings in his Tuesday debut for High-A Bradenton, allowing five hits and one walk while striking out seven, Pirates Prospects reports.
Keller primarily threw fastball after fastball in Low-A ball, but after a couple innings Tuesday he mixed in off-speed stuff. "More advanced hitters, obviously," Keller said. "So they were ready to hit the fastball. I think they knew what I was trying to do. We had to change it up a little bit earlier, and I think that worked." His curve ball and changeup aren't plus pitches yet, but his command of a mid 90s fastball has led him to success in 2016.