Walker, Arizona Diamondback

With the loss of Goldy, it seemed like there was a massive void at first base. The team’s plan to ride with a Jake Lamb/Christian Walker platoon was hampered when Lamb went down with a left quad strain in the 7th game of the season.

This plan is also being hampered by the fact that Christian Walker is hitting .347/.413/.722 (188 wRC+) with 7 HR, 13 RBI, and 13 runs and has easily been the best hitter on the team so far this season.

It should be pretty obvious that it is extremely unlikely that Christian Walker will continue to perform at this high of a level for the rest of the season - a .375 ISO and .429 BABIP are both very unsustainable numbers.

But that doesn’t mean that Walker won’t continue to produce as a good hitter for the rest of the season. Today we’re going to take a look at the three areas of Walkers offensive game - his power (via Statcast), batted ball profile, and plate discipline - and see what is and isn’t real.

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Statcast Power Data

We’ll start with the most obvious and prominent part of Walker’s game: his power. Christian Walker has power. Lots and lots of power. And so far, he is dominating the MLB in this category.

There are 261 batters with at least 30 batted balls so far this season. Here is where Christian Walker ranks among these 261 batters in a variety of Statcast-provided power stats:

These are really really impressive numbers - they are all 94th percentile or better. When it comes to hitting the ball hard, only Joey Gallo and Aaron Judge have a higher average exit velocity than Walker. For the Hard Hit balls (hits over 95 MPH), only Gallo, Judge, and Anthony Rendon are ahead of him. That’s really good company.

Walker does drop a bit when you incorporate plate discipline - specifically barrels/PA and xwOBA, both of which include strikeouts and walks into their rates.

But that’s not necessarily bad, either. Walker wasn’t supposed to be anything close to this good and while he’s due for regression, his xwOBA of .427 is a really good sign as it includes his 10% BB% and 28.8% K% into its calculation. And while this is below his current .462 wOBA, a .427 wOBA going forward is still roughly equivalent to a 160-170 wRC+, which is still an elite hitter.

The numbers behind Statcast’s formulas aren’t published, so we don’t know their stabilization points. There is no guarantee that Walker will continue to hit like a .427 wOBA hitter going forward, just that he’s hit like a .427 wOBA so far.

But power isn’t something you can fake. You can’t just “accidentally” hit the ball hard. You need to have the underlying strength and mechanics to actually hit a ball as hard as Walker does. Walker has clearly demonstrated that he has elite raw power. The question is whether he can continue to hit like this in games going forward.

So far, Walker appears to be in a good spot. His average launch angle is 14.3°, which is where you want to be. A higher average launch angle would mean that Walker was basing too much of his success off a high flyball rate (which, in the next section, you’ll see is currently in a good spot) and a low average launch angle means too many grounders. Walker’s success has been both in the pure power department (homers) as well as a good rate of line drives (which are singles, doubles, and triples).

As we’ll see in the batted ball section, Walker’s currently got a really healthy batted ball profile so far. The question again is sustainability - can he continue to hit line drives and singles while still maintaining his elite power? Can he do this without any further worsening to his plate discipline? We don’t really have the data or answers for that yet, but if there is one part of Walker’s game that is surely real, it is his raw power. That isn’t going anywere.

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Batted Ball Profile

Line Drive%: 22.4%

Groundball%: 38.8%

Flyball%: 38.8%

HR/FB%: 36.8%

ISO: .375

The mix of line drives, grounders, and flyballs, as mentioned above, is promising to see for Walker, because these are all numbers that are very sustainable - he’s not extreme in any one measure which would raise some huge red flags for regression going forward.

The flyball rate is important. Prior to this season, he had flyball rates of 57.1% in 2017 and 51.9% in 2018, albeit in small samples. While more flyballs are good for power and homers, those were numbers that were too extreme to be sustainable for most players. However, Christian Walker has mostly converted those flyballs into line drives, which is good for his BABIP.

By the eye test, Walker hasn’t looked like the all-power type that just jacks as many flyballs as he can to hope for homers. He looks to be a fairly well-rounded hitter and the stats, so far, are backing this up. This is a good sign.

However, the HR/FB% and ISO are both due for regression... but not as much as you might think.

HR/FB% is one of those stats that can be really noisy in small samples. In conjunction with BABIP, these two stats are the two primary drivers in hot/cold starts and the two quickest places to look for regression for any SSS player evaluation. And if you haven’t noticed a theme from last week, we have good predictor stats to judge how “real” the stats have been.

xHR/FB = -0.0066 + ([Fly Ball Pull% + Fly Ball Oppo%] * 0.0671) + (Brls/BBE * 1.2479)

So, just like we judged with Merrill Kelly’s HR/9 rate last week, we’re using the same stat this week but for a hitter. And this stat is very simple: it takes the rate at which a batter “barrels” up the ball (per Statcast) and adds it to the frequency at which a batter hits the ball to left or right field (since it’s harder to hit homers to center). Combine these three stats and it will estimate what a hitter’s rate of homers per fly ball should be.

In the case of Christian Walker, his xHR/FB% is still a whopping 28.6%. That’s really good. Last year, only Christian Yelich and JD Martinez had a HR/FB% over 28.6%. And while HR/FB% isn’t the sole measure to judge a player’s overall power, it’s still an overall good measure. Due to the small sample size, it’s pretty likely that Walker’s xHR/FB% will drop a bit over the course of the season, but it may not be a lot. It’s really promising that Walker hasn’t been over-producing too much on this metric so far.

Then of course, there is that .375 ISO which is extremely difficult to sustain. Last year, only Mike Trout (.316) and Khris Davis (.302) maintained an ISO over .300 for the season. A .375 ISO has been achieved before, but only 22 times in baseball history, with 6 seasons from Babe Ruth, 5 seasons from Barry Bonds, and 4 from Mark McGwire, and the rest are all one-timers.

So while it would be really awesome to see Christian Walker maintain this .375 ISO, it’s also extremely unlikely. Luckily, we have an xISO estimator:

xISO = (0.07069 * LD%) + (0.38573 * FB%) - (0.12343 * LDFBEV) + (0.00074209 * LDFBEV^2) + 5.083

Where LDFBEV = average exit velocity on line drives and flyballs.

Don’t let this equation confuse you. Essentially, it’s line drive rate + flyball rate + the average exit velocity on your line drives and flyballs. The harder you hit line drives and flyballs in combination with the frequency you hit line drives and flyballs leads to what your ISO is. This should be pretty intuitive.

And in Walker’s case, it’s good news. His current xISO is .317. That would have been #1 in baseball last year, one point ahead of Mike Trout.

However, as is the case with HR/FB%, it is fairly unlikely that Walker will continue to maintain a .317 xISO for the rest of the season. Both of these stats depend very heavily on Statcast data and Walker hasn’t gone through an extended slump yet or given enough time for pitchers to figure out his weaknesses and let this numbers average out a bit.

But Walker is in a really good place right now. Both these metrics show how real his power is. Both of these measures can drop by quite a bit and Walker would still be well above average. The projection systems only have Walker at .226 ISO at best (ZiPS), but Statcast is telling a much different story. Unless Walker’s approach and/or discipline massively crater, it’s looking more and more likely that Christian Walker is going to beat his projections, at least in the power department.

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Plate Disicpline

Last up is plate discipline, which is also the hardest to assess in small samples.

K%: 28.8%

BB%: 10.0%

We all knew Christian Walker was going to strike out a lot and 28.8% is a lot, but it’s significantly better than his previous seasons - 33.3% in 2017 and 41.5% in 2018, albeit in extremely small samples. For what it’s worth, ZiPS projects a 27.9% K% for Walker. We also have xK%:

xK% = 1.095 – (Z-Swing% * 0.250) – (Contact% * 0.888) – (Zone% * 0.076)

This formula is a bit counter-intuitive, as it doesn’t include the rate at which a batter chases pitches outside the zone (though that’s counted with Contact%). All three of these variables are negative which makes sense: swinging at more pitches in the zone, making more contact, and more pitches in the strike zone are all going to reduce the rate at which a batter strikes out. The R^2 for this equation is 0.8147 so it’s a very strong indicator.

In Walker’s case, his xK% is 29.2%, or right in-line with the 28.8% he’s posted so far. This is slightly higher than his projections but not unreasonably so.

It seems pretty safe to buy Walker at a ~28% - 30% K% going forward. It’s where he’s at now, it’s where the projections have him, and it’s where the estimators have him. Considering Walker’s immense power, a K% this high is fairly acceptable, but we should be concerned if it jumps over 30% for an extended period of time.

Walker’s walk rate is a bit harder to asses. We don’t have any good predictors for it. However, there is a bit of a promising sign: it appears that Walker might have made an adjustment from his past. Specifically, it looks like Walker might be swinging at less pitches:

We’re not working with much data, but this drop in Swing% has also coincided with a drop in O-Swing% (aka swings at pitches out of the zone) from 39.2% last season to 29.6% this season. It’s hard to say if this a real improvement for Walker or just SSS. But it’s clear that he’s reduced his swing rate considerably, especially compared to last year, which has been yielding better results for Walker. Furthermore, pitchers have been adjusting to Walker by throwing him less strikes, as he’s currently sitting at a career-low 40.9% Zone% (league average is 46%).

Zone% can actually be a really useful sign, as it indicates that pitchers are generally afraid to throw strikes to specific hitters. And usually, these changes come very quickly when a hitter has shown a significant improvement. This has actually been researched in depth, finding that a change in Zone% correlates with hitters outperforming their projections. So while we cannot use this information to conclusively prove that Walker is better than his projections, we can still use it as supporting info.

Back to BB%; while the Zone% on its own doesn’t tell us much, the lower Zone% in conjunction with a lower overall Swing% supports that Walker will be taking some walks. Walker has a career 8.6% BB% in the minors and he’s projected at 7.5%, so it’s not really that outlandish to maintain something around 10%, especially if pitchers continue to avoid throwing him strikes and he continues not to chase. A walk rate between 8.0% and 11% seems pretty “real” from Christian Walker right now.

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Christian Walker looks pretty real. There is obviously some room for regression, as is always the case in only 21 games, but every aspect of his offensive game looks to be “real” or at least “mostly real”.

• Walker’s raw power is absolutely real.
• Walker’s game power (raw power + batted ball profile) looks to be mostly real.
• His current plate discipline looks to be mostly real.

It’s still early in the season but it’s looking more and more like the Diamondbacks have a good player on their hands. We still need time to see if pitchers can find a hole in Walker’s game or if loses his approach and starts swinging a bunch or hitting the ball poorly. But the overall offensive profile for Christian Walker looks really promising as of right now. This author wouldn’t be surprised if Christian Walker put up offensive value at a similar level to Paul Goldschmidt this season... as shocking as that might sound.