Pitching prospects are the common currency of the prospect laden deal. In the Huston Street trade, the top pitching prospect returned was AA right hander R.J. Alvarez. Pitching is easier to throw into these type of deals because no matter how highly the team trading away the pitcher values him, he is still a throw away from missing a season or more due to injury. Just look at the Mike Adams deal. The Padres were hailed for getting back two well-liked prospects from the Rangers, but in the end they were still pitchers (Robbie Erlin and Joe Weiland) and have missed significant time since being acquired. None of this is meant to knock R.J. Alvarez in particular. Instead it highlights how well the Padres did by getting two solid position player prospects in addition to Alvarez. Bravo.
Anyway, on to the specifics about Alvarez. Let us start with his strengths and weakness assessed by Baseball Prospectus before the season started ($):
Strengths: Big arm strength; fastball is impact weapon; works mid-90s and higher with ease; good vertical life; shows quality slider in the mid-80s; attacks hitters; late-innings mentality.
Weaknesses: Delivery has effort; arm slot inconsistency; (now throwing from low ¾); slider can flatten out; shows both a curveball and changeup that don’t grade to average; command is below average at present.
They also go on to list his potential as being a setup man in the big leagues with a lower end projection of perhaps just a middle reliever. ESPN's Keith Law seems to also believe in Alvarez as a future major league reliever ($):
He's also a fastball-slider combo pitcher, destroying right-handed batters this season... but it's control rather than command. (Alvarez) could probably pitch in San Diego's pen next year.
If you are interested in hearing a chorus of similar thoughts, here is Minorleagueball.com's John Sickels chiming in:
He has overpowering stuff, featuring a 93-96 MPH fastball and a very good slider, reflected sabermetrically in outstanding K/IP ratios. Alvarez has two problems: erratic control, and high-effort mechanics that worry scouts. He has enough stuff to close if he can sharpen his command and should be at least an effective middle reliever if he avoids physical problems.
To get some full harmony, I will add Marc Hulet of Fangraphs with a comment from his preseason prospect piece:
The Scouting Report: Alvarez strength as a pitcher is his mid-90s fastball that can touch the upper 90s. He throws with a lot of effort and a low three-quarter arm slot. His slider has its moments but it’s too inconsistent to be considered an above-average offering at this point. It will be interesting to see if he commands the ball well enough to dominate Double-A hitters.
The Career Outlook: The lack of reliable secondary pitches could limit Alvarez is a set up role. However, should his slider become an above-average offering, he could develop into a ninth-inning man.
Given that there is so much consensus around what Alvarez does and does not bring to the table, I do not have anything else to add. The Padres have themselves a nice future bullpen piece that will be major league ready soon. Expect near year for Alvarez to be handled similar to Kevin Quackenbush. He will be a fixture in major league camp for Spring Training. He will initially not be on the 40 man roster. There will likely be some reason to call him up at some point and then he will get a chance to prove how well he can transition to the bigs. If he does well, he will stick around.