Diamondbacks are hoping to be the team that finally turns Taijuan Walker’s upside into results

The Diamondbacks have two pitchers with tremendous upside that haven’t translated into results in Robbie Ray and Archie Bradley. Yesterday’s trade added another name to that category as the Diamondbacks acquired Taijuan Walker from the Seattle Mariners. A mid-market team with a small-market payroll will be taking a lot of chances on players with that kind of upside in their cost-controlled years. Walker is no different than other pitchers the Diamondbacks have acquired in this category. The Diamondbacks have 6 starting pitchers that are 26 or younger: Matt Koch, Shelby Miller, Braden Shipley, Ray, Walker, and Bradley.

Walker came up the Mariners farm system as one of the game’s top pitching prospects and nearly became a Diamondback four years ago. Walker showed promise early in his MLB career and posted a 2.0 fWAR season in 2015 where he pitched to a 4.56/4.07/3.82 ERA/FIP/xFIP. The Mariners were hoping for him to take a step forward in Year 2, but while the ERA improved, his FIP and xFIP regressed due to a jump in HR/FB rate from 13% to 17.6%. While HR/FB luck can change on a given season, an increase in that number is not just bad luck but also bad pitching. Walker allowed 52 homers over the last two seasons overall and has issues pitching deep into games.

Walker has pretty good stuff overall. He throws a mid-90s fastball with good life and has a very filthy at times curveball. Goose from Lookout Landing added a bit of firsthand information for Diamondbacks fans regarding Walker:

Sounds similar to Robbie Ray, right? Both pitchers have very good fastball, but their careers hinge on the development of their breaking pitch although Ray’s is more useful than Walker’s on a consistent basis. The biggest concern is coachability, although that was one of the reasons why Mike Butcher was kept on the staff and his relationship with the pitchers. I have no idea what the deal was in Seattle, but that shouldn’t be a problem in Arizona where the slate is wiped clean. Walker is fairly good at limiting walks with only 6% of hitters he’s faced taking a free pass over his career, an uncommon thing with the other young pitchers in Arizona. While he’s capable of putting up solid strikeout totals, he isn’t going to put up the big strikeout numbers that Ray and Bradley can provide.

I stated in my initial analysis that Walker profiles with the upside of a #2/3 starter, with a floor of a #4. In the Diamondbacks rotation he probably slots in right after Greinke, Ray, and Miller as the team’s #4 to start the season. In Arizona, Walker should have an opportunity to thrive under a different voice and perhaps respond better to it. The Diamondbacks are playing for upside and traded away a very good player in order to get him. Walker is still very much a project pitcher and someone who the coaching staff needs to fix. From the guy’s post on the Snakepit, the theory is that the curveball is the key.

Data taken from tables on Brooks Baseball.

From the scatterplot, the overall year has very little correlation. However, a trend we see at the end of the year of his usage and curveball whiff rate trending upward the final three months, although that’s the time they sent him down to AAA to work on things due to a rough end of the first half carrying to a rough start of the second half. The overall trend line has a positive slope of 0.26, but an R squared value of 0.08. With a small correlation coefficient, I included 2015 as part of the sample size. I got very similar results overall, the slope jumping to 0.29 and R squared of 0.078. Curveball usage also causes a slightly negative effect on overall strikeout rate, so there is a finite limit he should try to throw a game although I imagine his 2015-16 numbers might hold very little predictive value on how he performs in Arizona.

The curveball is Walker’s best secondary pitch off of his fastball and he’s recently developed a splitter that’s serviceable, although if he really wants to develop that pitch he should call up JJ Putz. Moving to a new league where the pitcher has to bat and facing fewer hitters than he would in the American League, there is a natural expected uptick in performance. He will be moving from a pitcher friendly stadium in Safeco Field all the way to one of the most hitter friendly stadium in Chase Field. Walker does have some troubling HR/FB tendencies, although that may the result of hitters sitting on his fastball due to not being able to locate his other pitches. Walker has a solid track record prior to 2016, with SIERAs all below 4.00, so there is a belief for a possible bounce back with a change in scenery as was the case with Jean Segura last season.

Another thing Walker needs to improve upon is pitching from the stretch, which isn’t a unique problem for the Diamondbacks young pitchers. Shelby Miller, Archie Bradley, and Robbie Ray struggled with men on base, as Shoewizard posted this about Walker:

For those wondering, a 134 OPS+ is basically Paul Goldschmidt’s production at the plate in 2016 and 80 is Michael Bourn’s. League average is 105 and 96 respectively. Ray was 113/90 and Bradley 103/97. If Walker can figure out to pitch in the stretch closer to league average, the production should go up. I don’t have any idea what’s different from the stretch vs. no one on base as he could be tipping pitches by accident or simply isn’t locating. A change in scenery and a different pitching coach with a different voice could be the simple solution, although this trade is very reminiscent of the Diamondbacks acquiring Rubby De La Rosa two offseasons ago. Hopefully the results trend better this time.