Taijuan Walker was once a heralded prospect. His athleticism, projectable frame, and raw stuff stood out from the time he was drafted 43rd overall in 2010, at the age of 17. He eventually worked his way up to the 11th spot in the Baseball America Top 100 in 2014, and Mariners fans (like myself) were hoping he was going to become the Prince to Felix’s King.

That didn’t happen. Walker flashed brilliance at times. In seven starts from May 29th, 2015 through July 1st, 2015, Walker posted 51 strikeouts to just three walks over 48.1 innings. He’s pitched three complete games in his career, one of them an 11-strikeout, no-walk shutout against the Angels last September. Even his overall K/BB rates suggest past and forthcoming success, as he’s punched out 21.5% of hitters, while walking just 6.6%.

But just as he’s had periods of dominance, there have been times where he can’t get anyone out, in addition to some injury and work ethic concerns here and there. Overall, he has posted a 107 FIP- and ERA- (for those into run prevention) over his career — not bad, but not great. It is concerning that he has gotten worse every year, with his FIP- going from 99, to 102, to 120 from 2014-2016.

The biggest problem with Walker is his propensity to give up the long ball. I mentioned the good K/BB numbers, but those are somewhat counteracted by his unsightly career HR/9 rate of 1.36.

Then, as one of his approximately 12,394 trades this offseason, Mariners’ General Manager Jerry Dipoto sent Walker on his way to Arizona along with Ketel Marte, in exchange for Jean Segura, Mitch Haniger, and Zac Curtis. The chances of him ever being the (Fresh) Prince of Seattle have vanished. But what will he do in Arizona?

We often hear about “change of scenery” players, guys who just didn’t jive with their old team, or needed a fresh start. That may or may not exist, but if the player’s new park has anything to do with it, a relocation to Arizona seems unlikely to work in his favor. Safeco Field is no longer the pitchers’ haven it once was, but it’s friendlier than Chase Field.

Last year, Walker’s HR/9 rate ballooned all the way up to 1.81, which was the 5th highest among pitchers with at least 130 innings. Now, some of that is an inflated HR/FB rate of 17.6%. But even with a league-average rate of 13% he’d have had somewhere around a 1.30 HR/9, still much higher than would be ideal.

My question is: can this be overcome, realistically? Can Walker still be the ace he was once hyped as, or will his long ball problem hold him back? I went over to the FanGraphs leaderboards and, starting in 2000, sorted for seasons in which the pitcher in question had a K/9 between 7.50 and 8.50 and a BB/9 between 2.00 and 3.00, in at least 130 innings. I did this to find pitchers with similar K/BB numbers to Walker, because I am interested in guys with sold peripherals paired with a dinger problem.

From there, I sorted by HR/9, and isolated the seasons with a HR/9 of 1.30 or higher. That is somewhat arbitrary, but I chose it because it’s close to Walker’s career mark (1.36), giving us a little bit of room below that and plenty of room above if last year’s 1.81 mark is a sign of things to come.

Here are those players (warning: large table incoming):

Season Name IP K/9 BB/9 HR/9 HR/FB ERA FIP xFIP WAR
2016 Taijuan Walker 134.1 7.97 2.48 1.81 17.6% 4.22 4.99 4.28 0.6
2014 Marco Estrada 150.2 7.59 2.63 1.73 13.2% 4.36 4.88 4.19 -0.1
2016 Tyler Duffey 133 7.71 2.17 1.69 19.5% 6.43 4.73 3.89 1.0
2015 Anibal Sanchez 157 7.91 2.81 1.66 16.0% 4.99 4.73 4.03 1.0
2012 Phil Hughes 191.1 7.76 2.16 1.65 12.4% 4.19 4.56 4.35 2.4
2013 A.J. Griffin 200 7.69 2.43 1.62 12.5% 3.82 4.55 4.18 1.4
2015 Matt Shoemaker 135.1 7.71 2.33 1.60 14.0% 4.46 4.59 4.16 0.7
2011 Colby Lewis 200.1 7.59 2.52 1.57 11.9% 4.40 4.54 4.10 2.0
2010 James Shields 203.1 8.28 2.26 1.50 13.8% 5.18 4.24 3.55 2.0
2010 Ted Lilly 193.2 7.71 2.04 1.49 11.1% 3.62 4.27 3.95 2.5
2012 Ivan Nova 170.1 8.08 2.96 1.48 16.6% 5.02 4.60 3.92 1.5
2013 Chris Tillman 206.1 7.81 2.97 1.44 14.2% 3.71 4.42 3.88 1.9
2001 Eric Gagne 151.2 7.71 2.73 1.42 9.2% 4.75 4.62 – – – 1.3
2008 Ted Lilly 204.2 8.09 2.81 1.41 12.1% 4.09 4.41 4.08 2.8
2016 Jake Odorizzi 187.2 7.96 2.59 1.39 12.0% 3.69 4.31 4.44 2.0
2009 Joe Blanton 195.1 7.51 2.72 1.38 12.9% 4.05 4.45 4.02 2.2
2016 Jaime Garcia 171.2 7.86 2.99 1.36 20.2% 4.67 4.49 3.77 1.2
2016 Jason Hammel 166.2 7.78 2.86 1.35 13.8% 3.83 4.48 4.34 1.4
2011 Max Scherzer 195 8.03 2.58 1.34 12.6% 4.43 4.14 3.70 2.2
2015 Taijuan Walker 169.2 8.33 2.12 1.33 13.0% 4.56 4.07 3.82 2.0
2009 Aaron Harang 162.1 7.87 2.38 1.33 11.7% 4.21 4.14 3.88 2.6
2015 Drew Hutchison 150.1 7.72 2.63 1.32 12.7% 5.57 4.42 4.21 1.5
2011 Chris Capuano 186 8.13 2.56 1.31 12.0% 4.55 4.04 3.67 1.9
2016 Zack Greinke 158.2 7.60 2.33 1.30 13.9% 4.37 4.12 3.98 2.2

Off the bat, you can see that Walker is at the top when you sort by HR/9. That’s something to keep in mind – in one sense, he has even farther to go to get back to an acceptable level. However, it may also suggest he got unlucky to a degree and may have some natural regression coming his way.

The more important discussion is how well we can expect him to do going forward. Below you can see what the above pitchers did for the rest of their career (note: several of the above seasons were from 2016, so they obviously won’t be represented):

Name G GS IP K/9 BB/9 HR/9 HR/FB ERA FIP xFIP WAR
Eric Gagne 344 0 360.2 11.95 2.62 0.72 9.4% 2.57 2.44 2.56 12.1
Max Scherzer 164 164 1079.1 10.70 2.24 0.98 9.8% 3.09 2.96 3.15 27.7
Matt Shoemaker 27 27 160 8.04 1.69 1.01 10.3% 3.88 3.52 3.86 3.3
Phil Hughes 101 97 569.2 6.87 1.37 1.26 10.3% 4.44 3.93 3.99 8.4
James Shields 200 200 1316.2 8.03 2.72 1.14 12.8% 3.65 3.98 3.72 16.1
Joe Blanton 210 90 696.2 7.78 2.09 1.34 13.7% 4.55 4.06 3.63 6.2
Ted Lilly 103 103 635 7.43 2.27 1.26 10.0% 3.60 4.09 4.06 8.7
Chris Capuano 135 69 466 7.57 2.88 1.14 11.5% 4.36 4.09 3.99 4.2
Ivan Nova 76 67 416 6.88 2.40 1.10 13.9% 4.22 4.21 3.94 4.8
Chris Tillman 95 95 552.1 6.68 3.19 0.98 9.6% 3.99 4.22 4.43 6.5
Marco Estrada 63 57 357 7.46 3.03 1.18 9.3% 3.30 4.28 4.79 4.8
Aaron Harang 169 167 982 6.59 3.14 1.07 9.2% 4.28 4.29 4.49 7.7
Colby Lewis 97 97 596.1 6.66 1.99 1.30 10.1% 4.41 4.33 4.52 6.3
Drew Hutchison 9 3 24 8.25 2.63 2.25 19.4% 5.25 5.69 4.59 0.0
A.J. Griffin 23 23 119 8.09 3.48 2.12 16.9% 5.07 5.74 5.01 -0.1
AVERAGE 121 84 555.1 7.93 2.52 1.26 11.7% 4.04 4.12 4.05 7.8 2.5 WAR/180

There’s a pretty wide range. The best FIP is from Eric Gagne, but he did that as a reliever (maybe that would be a good path for Walker?). The best case scenario is easily Max Scherzer, who has rebounded to win two Cy Young awards (2013 and 2016) despite periodically struggling with dingers. That’s obviously a long shot for Walker, but he could also become James Shields, Matt Shoemaker or Phil Hughes, none of whom are necessarily the ace-level starters many hyped Walker to be, but are (or at least have been) steady #2/3 starters who still give up their share of home runs but do other things very well.

On the other end of the spectrum we have A.J. Griffin and Drew Hutchison and their respective FIPs of 5.74 and 5.69, also giving up over 2.0 HR/9. Griffin has dealt with injuries and Hutchison only has a 24-inning sample, but if Walker were to end up like either of them it would be a pretty substantial disappointment.

But those are the extremes, so now let’s look towards the middle. The averages are listed along the bottom, including WAR per 180 innings. I added that because of how much variance there is in innings pitched; it gives us a general snapshot of what these guys did (or would have done) in a full season as a starter.

The group’s FIP sits at 4.12, their HR/9 at 1.26 and their WAR/180 at about 2.5 wins. None are particularly impressive, especially the HR/9, but they aren’t horrible either. For comparison, the average FIP, HR/9 and WAR for our first list was 4.42, 1.48 and 1.8, meaning that, in general, they ended up improving. WAR wise, that’s essentially the difference between 2016 Martin Perez and 2016 Mike Leake. Not insignificant, but not a jump to top of the rotation status either.

Of course we can’t possibly know where Walker will end up. The pitchers in our sample vary so much, in age, stuff, makeup, and anything else you can think of, all of which certainly play a role in one’s ability to improve their game. The sample includes Ted Lilly from age-33 to age-37, for example, who was a far cry from age-27 to age-32 Scherzer.

In a similar vein, it’s worth noting that Walker is younger now than any of the other pitchers were when they had their seasons in question. He has time to figure things out. But this study seems to suggest that he will always run a relatively unsightly home run rate. Of our sample, only Gagne, Scherzer and Tillman ended up getting their HR/9 under 1.00, and their rates weren’t quite as bad as Walker’s to begin with.

Walker’s youth, velocity and athleticism are certainly all points in his favor, but I personally don’t expect Walker to ever come close to reaching his ceiling. Even if he dials the strikeouts up and cuts the walks even more, he figures to remain dinger-prone (especially in Arizona), and that will hold him back. He could still be a nice #3, but any more than that would require some drastic and unlikely changes.

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