D-backs' Rotation Depth is Stretched Thin, With No Help Coming Soon
The Diamondbacks could be in trouble if they lose any of their current starting five, with no Triple-A arms showing clear signs of MLB readiness.
The Diamondbacks find themselves in a precarious position regarding their depth in starting pitching. I’ve already taken a snapshot of the current starting five, which has shown encouraging results in the last turn.
Much of their rotation depth this season has been thinned out due to injuries. Four starting pitchers have undergone the knife this season. Two of them were depth pieces in Blake Walston and Tommy Henry, which have impacted their Triple-A rotation.
The injuries have opened the door for prospects Dylan Ray, Yu-Min Lin, and Spencer Giesting for an opportunity in the minor league’s highest level. Bryce Jarvis, at his request, was converted back to a starting pitcher. Those four young arms represent the next wave of arms expected to contribute to the rotation, as early as next season.
Basic Stat Outlook
Here’s a preliminary look at the performance of these four pitchers, based on the opening stats I like to use to evaluate Triple-A pitchers.
The first takeaway you probably had is that none of these pitchers should be in the major leagues anytime soon due to bad ERAs. However, it’s important to establish context behind the ERA totals, as the Pacific Coast League is a different run-scoring environment than the major leagues. The average runs scored per game in the PCL is 5.82.
With that in mind, it’s important to look past ERA metrics and pay more attention to their peripherals and quality of contact. That is exactly why the table above includes strikeout, walk, hard-hit (exit velocities north of 95.0 MPH), and barrel rate per batted ball. That to me is a bigger indication of how the pitchers are performing.
The issue here is that none of the four pitchers are exceptionally good at missing bats, coupled with an issue with limiting walks. Only one of the four pitchers has a walk rate below 10% (Ray) and one with a strikeout rate above 20% (Jarvis). If you subtract their walk rate from their strikeout rate (K-BB%), no pitcher is above 10%. Of the two most fundamental things a pitcher can control, none of the four pitchers are measuring up right now.
Jarvis would be the most likely arm to get promoted to the rotation in the event of an injury, given he’s already on the 40-man roster and is the most experienced arm. However, he’s pitched the majority of his career as a short reliever with the occasional long relief outing.
However, it’s important to notice that Ray and Giesting have a total of 9 starts in Triple-A. There’s still a lot of improvement for the two pitching prospects, and both of them have some promising signs.
Statcast Analysis
The analysis could stop here, and maybe that satisfies your curiosity there but since we have Statcast data for the Triple-A level. We can look at the batted ball metrics and see if any of them are getting hit hard in terms of exit velocity and surrendering the type of contact that leads to runs.
Bryce Jarvis
Starting with the most experienced arm of the group, Jarvis has the best raw stuff. The changeup and slider have been legitimate above-average offerings for the major league level, but he’s never found the right mix for fastballs to set up those two pitches. Part of that has to do with a flat four-seam shape (12.1 vert, 9.6 horizontal).
He’s added a sinker and cutter to his arsenal over the last two seasons to help offset a subpar four-seamer. The sinker has had decent success at inducing weak contact, with a 21.4% hard-hit rate against right-handed hitters. He hasn’t quite figured out the arsenal against lefties, something he needs to figure out to have any hope of sticking as a major league starter long-term.
Against lefties, he’s very reliant on the changeup. It gets a healthy amount of whiffs (28.8%) and keeps the ball off the barrel, but he’s giving up a lot of singles on it. He’s going to have to find something he can throw in the zone. The four-seamer and cutter have been obliterated in the zone, yielding a .381 average and .905 slugging percentage.
Spencer Giesting
Giesting does the best job at getting weaker contact, with a 32.3% hard-hit rate and an 8.1 barrel rate. That likely explains why he has the lowest ERA despite the worst walk rate and strikeout rate of the group. He has the lowest chase rate, at 18.9%, but those chases turn into whiffs at a 52.9% clip.
The key for Giesting is to put himself in a position where he can pressure hitters into chase. That means jumping ahead in the count 0-2 or 1-2 to put the hitter on the defensive. Giesting hasn’t been great in that area, as he’s only converted 15 of 42 (35.7%) 0-1 counts to 0-2 and 15 of 36 (41.7%) 1-1 counts to 1-2. The Triple-A averages are 42.7% and 44.8%.
Dylan Ray
Ray has been hit the hardest, with a 45.6% hard-hit rate and a 15.6% barrel rate. It’s likely because he’s the most aggressive pitcher in attacking the strike zone. 52.4% of his pitches are in the Gameday strike zone.
However, that’s led to a lot of pitches in the middle of the strike zone, as 28.1% are in the “Heart” Attack Zone. Ray doesn’t necessarily have the fastball to challenge hitters, so it will be incumbent on him to work closer to the edges.
When he’s closer to the edges, he gets good results. Ray holds opposing hitters to a .167 average and .333 slugging percentage on strikes in the shadow zone. The barrel rate drops to 4.5% despite a hard-hit rate of 50.0%.
Yu-Min Lin
Lin falls into the same category as Giesting, but with a lesser fastball. While the velocity is higher, averaging 90.9 MPH, he has a much flatter shape. It’s hard to tell if there are some misclassified sinkers in that grouping, but since he only gets 9.4” of induced vertical break on his fastball, it’s worth exploring more.
The walks have been an issue at the Triple-A level, as he’s put 13.3% of hitters on base. He’s had difficulties throwing strikes with the fastball and cutter this season, as the two pitches have yielded a .381 average and a .714 slugging percentage. That’s made him more hesitant to attack the zone early in the count, with only a 40.1% first-pitch strike rate.
The problem with that approach is his secondary stuff is more effective as chase offerings. The changeup is his best in-zone offering of the group, with a whiff rate of 32.7% and holding opposing hitters to a .154 average and .192 slug.
The key for Lin is to find a way to throw strikes early in the count to jump ahead of hitters then finish them off with his good secondary pitches. It’s more difficult with a bad fastball, so he’ll have to rely on tricking hitters and stealing strikes with the curve and sweeper before punishing them with the changeup.
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