Justus Sheffield called up, Shawn Armstrong DFA’d: managing the roster and expectations

The Mariners made two moves today, one expected and one less so:

First, the slightly unexpected move: designating Shawn Armstrong for assignment. Armstrong had struggled in the four-ish innings he pitched this year as he worked back from an oblique injury, with truly dreadful-looking peripherals, but given the small sample size and injury, as well as more encouraging numbers from last year and an off-season spent dedicating himself to the Mariners’ use of analytics—going so far as to purchase a Rapsodo machine for the North Carolina facility where he trains (something Mariners prospect Max Povse was also able to benefit from)—it’s surprising that the 28-year-old found himself on the outs ahead of someone like 33-year-old Cory Gearrin, who has had some well-documented command issues, or lefty specialist Zac Rosscup, whose 12.86 K/9 would be impressive except for it being partnered with a BB/9 that’s barely a point lower. Perhaps the Mariners are rolling the dice on sneaking Armstrong through waivers a second time, wagering that their in-house knowledge of his improvements isn’t shared by other teams who will only see a recently-injured, ineffective reliever. Both Rosscup and Gearrin have lengthier major league track records and might be more appealing bait. At any rate, we’re hoping Armstrong clears waivers and remains with the organization, not only because we believe he’s due to rebound, but because Armstrong seems to be an absolute mensch, between his stoic acceptance of a lengthy Tacoma assignment last year despite pitching well because of roster flexibility issues, and this from Manny Acta:

The Mariners had two choices to make space for Sheffield, who will in turn be optioned after his appearance tonight to make space for newly-acquired reclamation project Mike Wright: they could option Chasen Bradford, who is the team’s fourth-best reliever by fWAR and the best at getting groundballs behind Brandon Brennan; or DFA a player. Sending down Bradford would mean he’d have to remain in Tacoma for 10 days except in case of injury, so rolling the dice on Armstrong made more sense, especially given that he’s probably at his lowest conceivable value as a player.

As for Sheffield, tonight will mark his Mariner debut. While he’s not technically the starter, Yusei Kikuchi will serve in more of an “opener” role, going no more than a couple of innings (although the Mariners have played coy at announcing how many innings that will be, exactly), at which point Sheffield will take over. Ideally the Mariners will score a few runs early to give their rookie pitchers a comfortable lead. We’ve already seen quite a bit of Kikuchi, but here’s what to watch for with Justus Sheffield’s debut:

• Fastball command. This is the biggie, and something that’s been troubling him in Tacoma, where he’s walked at least three in each of his outings. It’s an interesting contrast to his performance in Spring Training, where he only walked one across his four innings while striking out six. Sheffield was also dominant on the backfields, including in scrimmages against his major-league teammates, who described his stuff as “nasty.”
• The changeup. The biggest surprise for me in watching Sheffield this spring was how effective his changeup was. Supposedly the third pitch in his arsenal along with the plus-velocity fastball and hard, sharp-breaking slider, the changeup had a moment of its own this spring, with Sheffield able to use it as a swing-and-miss pitch. Some of Sheffield’s current struggles with command might be from attempting to adjust his pitch mix to include more changeups; we’ll dig into this next week with the benefit of some accurate location and velocity info from his appearance tonight.
• Pitch mix. The fastball has been Sheffield’s calling card over his lengthy high-profile career as a prospect, but as Jake examined, it’s really not his best pitch from a swing-and-miss standpoint. While I’ll expect Sheffield to lean heavily on his fastball, I’ll be most encouraged by an outing in which he feels comfortable enough to mix in his secondaries more the second time through the order. That could be a challenge if the fastball is poorly located his first time around, making the fastball command all the more important. However, I’d rather see good process and potentially poor results over Sheffield using his fastball as a crutch.

It’s not ideal for Justus Sheffield to be making his Mariners debut tonight. Sheffield has a high ceiling and showed flashes of brilliance this spring, but he’s very much a work in progress, unlike his more polished counterpart Erik Swanson. There’s a very good chance Sheffield struggles tonight, in which case there will probably be a fair amount of shade thrown about the return for James Paxton, who’s currently coming off two back-to-back dominant starts and has posted a career-low FIP and career-high K/9 over his first five starts. Justus Sheffield is going to take some time to reach his ceiling, which makes sense, as he’s eight years younger than James Paxton. Meanwhile, don’t let a (potentially) rough first start as a Mariner and the inevitable snarky tweets distract you from the fact that Erik Swanson (25) has already had two solid starts at the major-league level, and Dom Thompson-Williams (24) has a 115 wRC+ and a .174 ISO in his first taste of Double-A.