Phillies rookie Jerad Eickhoff: How good can he be?

From the Minor League Ball mailbag:

"Jerad Eickhoff. Huh? Worth a fantasy investment?"---Adam B.

Eickhoff was a rather anonymous arm in the Texas Rangers farm system until his inclusion in the Cole Hamels trade, but his performance down the stretch for the Philadelphia Phillies was excellent: 2.65 ERA in 51 innings, 49/13 K/BB, 40 hits, 3.25 FIP. The innings count pushes him past technical rookie limits so he won't show up on most prospect lists entering 2016. That might make him fall through the cracks in some fantasy situations, but yes he is probably worth an investment.

This was my take on him pre-season in the 2015 Baseball Prospect Book:

The Rangers drafted Eickoff in the 15th round in 2011 from Olney Central Community College in Illinois. He hasn’t received a lot of attention but he did have a good 2014 season in Double-A, showing a low-90s fastball (occasionally a little higher) with a good curve and an adequate change-up. He’s a fly ball guy and gopher-vulnerable when he makes a mistake with location, but he eats innings and stays healthy, which covers many sins. He could see major league action as a fifth starter or bullpen reinforcement type. Grade C.

That was based on his 2014 season which saw a 4.08 ERA on 154 innings in Double-A, but with a decent 144/52 K/BB. In the minors this year he posted a 3.86 ERA with a 126/39 K/BB in 133 innings.

Within the context of his entire career, what Eickhoff did with the Phillies was just past the upper-bound of expectations. He pitched like a sound number three starter (if not a number two), but the minor league track record showed him as more of an inning-eater number four or five type, albeit an efficient one with good control.

Why did this happen?

There was no magical increase in fastball velocity: his heater was 88-94 in the majors, averaging about 91, which is exactly what it was in the minors. In the Rangers system in 2014 his breaking ball looked to my eye like a decent slurvy curve. The change-up was okay but not as good as the fastball or breaker. He looked like a back-end starter, just as the numbers would imply.

However, Eickhoff's secondary stuff took a big step forward this year. The breaking ball is now viewed as two distinct pitches: a power curve and an effective slider, both pitches described very well by Paul Sporer at Fangraphs in a recent article. I'm not sure if Eickhoff made a deliberate decision to develop two different breakers, but either way the breaking stuff he showed with the Phillies has considerably more bite than what he showed in 2014. The change-up is still mediocre, definitely a fourth pitch. He doesn't use it nearly as often as the fastball, curve, and slider, but it is there to give hitters a different look.

Sporer points out that Eickhoff had a very sharp platoon split despite his big league success, something that will catch up with him eventually as a starter. That said, Eickhoff has clearly shown the ability to adapt and improve. He's big (6-4, 240), throws strikes,and obviously pitched well enough to make a strong claim on a rotation spot heading into 2016.

My guess is that "solid fourth starter" is still the most likely long-term outcome here, but do keep in mind that Eickhoff fits many of the criteria we look for when hunting for sleepers. If he can improve the change-up or sharpen his command from good to excellent, he could continue to exceed expectations.