What to Watch for Diamondbacks Prospects in the Arizona Fall League

The season opener for the Salt River Rafters begins Tuesday. Eight players in the Diamondbacks organization are expected to compete over the next six weeks. It will be an opportunity for all eight players to replace lost reps. In turn, that should add more clarity to the organization on what their future plans for them should be.

Here's a primer on what I'd like to see from the eight players in the Arizona Fall League.

Drey Jameson Needs to Show Good Health

This is more or less a glorified rehab assignment for Drey Jameson. The 28-year-old fireballer needs to throw the ball cleanly and without pain. His fastball averaged over 98 MPH during the regular season, so we have a baseline to compare. He'll need to sit in that upper-90s range, with the occasional 100+ MPH reading.

More important than the velocity will be the command. With less rise than a typical fastball, he'll have to rely on locating it at the top of the zone for swings and misses. Jameson can also use his mid-90s sinker, which is better suited to attack hitters in the zone than his four-seamer. Establishing the ball-to-strike tunnel glove-side (back door to RHH, front door to LHH) will help set up his slider.

The slider is still Jameson's best swing-and-miss weapon. The pitch generated a 49.0% whiff rate and 37.8% putaway rate (two-strike pitches that result in a strikeout) in Triple-A. It should play well against most of the hitters in the fall league, who haven't necessarily dealt with Jameson's velocity or stuff.

The changeup is an interesting pitch to keep an eye on. It's a pitch he's never really mastered much in his career, but could give a different look to lefties. For now, it's not necessary to establish himself as a big league reliever. But it's something on the back of my mind to monitor, as it could determine his viability as a back-end arm.