Miller jumped out of the gate in AFL action with an impressive early stat line of 16 strikeouts against a single walk and four hits over his first nine innings pitched, including eight in the 3.2 innings I was able to see in live views on October 11 and 14, both vs. the Peoria Javelinas.
He was converted to a relief role just this year, and even with four minor league promotions under his belt (beginning with Class A Kane County and ending with Double-A Mobile after a five-appearance stop at Triple-A Reno in August) he’s still thrown roughly half of his 2015 innings total (119.1 in 2015 vs. 61.1 this year).
An 11th-round pick of the Diamondbacks out of pitching factory Vanderbilt University, Miller lives down in the zone, and the approach has been working for him, with a 3.39 GO/AO ratio across four levels in 2016, though below-average control (BB/9 rate of 3.4/9) has been an issue. He does get a monster share of strikeouts though, (11.7/9), and he held opponents to a .169 BAA while giving up just three home runs (two during his stint in Reno) in 61.1 innings, so getting some more relief experience and cutting down on the walks was probably the goal of his AFL stint.
Miller creates some angle both with his six-foot-seven height and with his mechanics. There are some moving parts to the delivery, with some shoulder tilt and slight spine tilt to the third base side clearing the way for a long arm action with a stab in the back that comes quickly through a high 3/4s arm slot with some head whack to-boot. The high-effort actions are probably causing some of his control issues, but Miller showed the athleticism to keep them in sync and repeat them in these views, and those same actions can also make it tough to pick the ball up out-of-hand, so the delivery can work for him if he can improve on repeating it.
His fastball generally sits in the 91-to-93 mph (T94), though in his first outing he was more reliant on a cut version that was sitting 87-to-90 mph. Both versions play up to above-average offerings thanks to the downhill plane he gets to change eye levels, and he commanded both variations down in the zone for strikes to set up his slider and curveball, both of which looked to be average-or-better secondaries in these views. The slider was sitting 82-to-85 mph in both views, and was his best breaking pitch, showing 3/4’s depth and bite out of a fastball plane, with the angle playing it up some. He was confident using the pitch in any count, both for strikes when needed, and for put-away, and it also generated some swing-and-miss. He did leave a couple hanging in the zone, which is something he won’t get away with at the higher levels, but overall it was an average offering that could get to above-average with improvement to the command. He also showed good feel for his curveball, sitting in the 77-to-79 mph with an 11-to-5 plane and with big shape and late downer action, and also using it as a chase pitch.
With starting pitchers rarely throwing more than three innings in AFL action, there’s plenty of opportunity for Miller to gain some experience in his new role. He has the ingredients to be a solid middle reliever for the D’Backs, though a little more proof-of concept seasoning and some stabilizing/fine-tuning of his mechanics at Triple-A Reno might be in order to start the year. If he can show that the improvements seen in his AFL appearances are here to stay, he could be a candidate for a spot in the bullpen as soon as mid-year.