Heading in Opposite Directions: Paul Goldschmidt and Christian Walker

The day after the regular season ended, MLB.com’s (and FanGraphs alum) Mike Petriello posted the following tidbit on Twitter.

Have to admit, "Paul Goldschmidt & Christian Walker having almost the exact same season" is not exactly what I expected after the ARI/STL trade:

Goldschmidt
.260/.346/.476
.346 wOBA
11% BB
24% K
.216 ISO

Walker
.259/.348/.476
.346 wOBA
11% BB
26% K
.217 ISO

— Mike Petriello (@mike_petriello) September 30, 2019

Like Mike, I was surprised by the similarities between the Diamondbacks’ former and current first basemen. I was well aware that Paul Goldschmidt had taken a step back this season, and I also knew that Christian Walker had acquitted himself well as Goldschmidt’s replacement in Arizona. Even so, it didn’t occur to me that this pairing could create a dilemma on draft day in 2020.

Those who responded to a Twitter poll I published seemed to have a similar reaction. In asking which of these first basemen respondents would rather draft next year, Goldschmidt was the overwhelming favorite. There are some obvious reasons to rank him ahead of Walker: a longer track record, a demonstrated high ceiling and, despite the similar skill profiles, Goldschmidt returned more than $5 in standard Roto value than Walker did this season. Some but not all of that discrepancy is due to differences in playing time, which I will address further down.

(2/2) Poll: So…which player would you rather have in #fantasybaseball in 2020, assuming you could draft them at a similar position: Goldschmidt or Walker?

— Al Melchior (@almelchiorBB) October 3, 2019

At 28, Walker is not a strong candidate to grow into an even better skill set, but in being three-and-a-half years younger than Goldschmidt, he is not as strong of a candidate to decline. This season, we may have already begun to see Goldschmidt’s descent. This was not like 2018, when he produced a .719 OPS and a 96 wRC+ through the end of May, only to rebound with a 1.022 OPS and 171 wRC+ the rest of the way. In 2019, Goldschmidt posted a wRC+ of 125 or lower in four of the season’s six months (lumping March and April together), and his overall 116 wRC+ is the lowest full-season mark of his career.

The decline was particularly apparent against right-handed pitchers. Between 2015 and 2018, Goldschmidt’s average exit velocity on flyballs and line drives (EV FB/LD) hovered between 95.5 and 96.1 mph, with the exception of 2016, when it dipped to 94.3 mph. That year, Goldschmidt turned in a disappointing 120 wRC+ against righties and a 133 RC+ overall. That looked like an aberration in his age-28 season, but this season, as a 31-year-old, his 94.1 mph EV FB/LD and 108 wRC+ against righties look more ominous. His decrease in exit velocity is even more disconcerting, given the presence of the “rabbit ball.”

While Goldschmidt’s .199 ISO against righties was only his third sub-.200 mark in his nine-year career, his .298 ISO against lefties was the second-highest of his career. Even here there is cause for concern, as his 95.8 mph EV FB/LD is one of only two marks against lefties below 97.0 mph since 2015, with 2016 once again being the other outlier.

In 2018, Goldschmidt lost his appeal as a source of stolen bases, and this year, it appears that his power is eroding. It was also the first season since 2012 that his batting average fell below .290, and at .260, the drop was substantial. His .250 xBA against righties was actually lower than his actual .258 batting average, but against lefties, he sported a .296 xBA (as opposed to his .269 batting average).

Meanwhile, Walker averaged 95.2 mph in exit velocity on flies and liners, which was good enough to rank him 32nd out of 175 batters with at least 300 total batted balls. He also ranked 43rd with an 88.0 mph average exit velocity on grounders, which helped him to finish with a .312 BABIP — 14 points above the major league average. There is nothing suspicious about any of the components of Walker’s .259/.348/.476 slash line, other than the worry that pitchers will adjust to him in 2020. However, there was no such dropoff over the season’s final three months, as Walker maintained his .217 ISO from the first three months while improving both his strikeout and walk rates.

Unless you are unconcerned about Goldschmidt’s loss of power and steals in his early 30s, as well as this season’s drop in batting average against righties, this comparison so far would point to passing on Goldschmidt and targeting Walker (or someone else) in next year’s drafts, assuming that Walker is still on the board. However, Goldschmidt did hold advantages in plate appearances (682 to 603), RBIs (97 to 73) and runs (97 to 86). The difference in runs can mostly be chalked up to differences in playing time, but Walker’s .222 Avg with runners in scoring position contributed to his shortfall in RBIs. Both players spent much of 2019 hitting in the heart of their respective teams’ batting orders, but Goldschmidt hit nearly as well with RISP (.252) as he did otherwise (.262). Unless there is a particular reason to think Walker is not clutch, we should expect his run production to improve next season.

It’s really too early to assume anything about the team contexts for either Walker or Goldschmidt in 2020, but I should note that the Diamondbacks did outscore the Cardinals, 813 to 764, this season, and they did so without Steven Souza Jr., and with an injury-plagued David Peralta. They will also get more playing time from Carson Kelly and possibly from Walker himself. He started 132 games, as he had to split time with Jake Lamb at various points during the season, but Walker proved to be the superior hitter. With a .340-plus wOBA against both righties and lefties, he is not a candidate to be platooned. Unless the Diamondbacks want an upgrade over Walker’s 2.6 UZR/150 at first base, he should play more next season, giving himself a chance to improve his counting stats. A 30/90/90 season is far from out of the question.

It’s understandable that owners will likely be more comfortable drafting Goldschmidt than Walker in 2020. Goldschmidt could have a mild rebound, and there is no disputing his playing time. However, the difference between him and Walker may be smaller than we are inclined to think it is.