Pat Reusse has a column today on Randy Rosario, left-handed prospect (and project) pitcher. I saw Rosario last August in Cedar Rapids and wrote this.
Reusse quotes Rosario on his pitches: A high velocity but straight fastball and a wipeout slider. That matches what I saw in August.
The Twins want to develop Rosario as a starter, and that's both sensible and understandable. There's more value in a starter than in a reliever, and even if he winds up in the bullpen, he'll get more innings, more chances to develop his pitches, as a starter. He hasn't pitched above the Midwest League yet.
But ... we have an injury history, we have a (at this point) limited set of pitches, and we have an option clock that will start clicking this spring. My guess is that he's destined for the bullpen, and I really wouldn't be dismayed if it happens sooner rather than later.