Minor League Ball Ranking: 10th (Rangers)
Minor League Ball Grade: B-
MLB Pipeline Ranking: 8th (Brewers)
MLB Pipeline Tools Grade: Fastball- 70; Curveball- 65; Changeup- 45; Control- 50; Overall- 50
Corey Knebel is a 23 year old right handed reliever originally drafted by the Tigers in the first round of the 2013 draft (39th overall). He split 2014 between AA and AAA with the Tigers and the Rangers. In addition he threw a handful of innings at the major league level before being shut down in August with a strain to the ulnar collateral ligament in his elbow. Yes that's the Tommy John ligament.
The Brewers medical staff signed off on Knebel so he's presumably healthy. Assuming that's the case it appears very likely that he'll join the Brewers bullpen on Opening Day. He would appear to be the late inning relief help they've been looking for all off-season.
There is a consensus about Knebel among talent evaluators. The kid has high leverage "closer" potential. He has 2 above average to plus pitches. His fastball sits around 94-95 and can be ramped up to 98. His curveball is in low 80s with "sharp downward break" that provides nice separation in speed between the two offerings. His delivery is "funky" and max effort. That adds deception but it also increases his injury risk. And that's the thing.
Along with that consensus is a caveat: If healthy. He has all the tools necessary to be an excellent reliever. It's just a matter of staying healthy. More to the point, after his elbow sprain it's a matter of staying off the operating table.
A sprain by definition is a tear. Corey Knebel tore his ulnar collateral ligament in 2014. Let me put it another way. Corey Knebel tore his Tommy John ligament in 2014. Now, I don't mean to be too alarmist. It's entirely possible he's fine and goes his whole career without needing any kind of surgery.
His injury could have just been a "Grade 1" sprain which is a stretching of the ligament which remains intact. The Brewers are well known for the quality of their medical staff. If they gave the okay on Knebel they must be confident in his health. All I'm acknowledging is that Corey Knebel has some injury red flags.
Health aside, Knebel is a solid upgrade from David Goforth, the Brewers until recently top relief prospect. For comparison Goforth's grades according to MLB Pipeline are: Fastball-70; Cutter-50; Curve-45; Change-45; Control-45; Overall-45. Goforth is also half a season to a year away from reaching the majors. This isn't to say Goforth is bad. Quite the contrary. I'm pointing out that the Brewers now have 2 young relievers with high leverage potential that sit 94-95 and can hit 98.
Then there is Jeremy Jeffress at the major league level who also has a big time fastball. Also, if they rebound from their respective injuries, the Brewers could add Jim Henderson and Johnny Hellweg to that elite fastball discussion. That's potentially 5 relievers capable of hitting the high 90's and potentially capable of handling high leverage situations under cheap long term team control. Keyword being "potentially."
That's without even mentioning the potential with Will Smith and Tyler Thornburg. If everything works out the Brewers could actually have built a pretty enviable bullpen staff. Of course Knebel, Henderson, Thornburg, and Hellweg all share serious injury red flags or are currently recovering from injury. So while the potential is high, so is the risk.