Taijuan Walker, despite a very strong spring, has struggled mightily so far this season. His ERA sits above 8.00 as I write this post.
Like any pitcher with such a woeful ERA, Walker is the "victim" of "bad luck." In other words, there are rates in his stats that should be unsustainable. For instance, Walker has only stranded 58.3% of baserunners (unsustainably low), yielded a .386 BABIP (unsustainably high), and sports a 15.3% HR/FB rate (extremely high, and unlikely to stay so high).
That's lazy analysis though. Just assuming that Taijuan Walker will get better through the magic of regressing to the mean is dangerous. The idea of regressing to mean presupposes that Walker should act like the majority of the MLB starting pitching population. Let me explain further with an absurd thought experiment. What if I told you that I had an unsustainably high HR/FB rate in the major leagues? You'd double over laughing, or at least I'd hope you would. I would be a glorified batting practice pitcher against MLB competition, and I bet batters could muster an "unsustainable" home run rate against me.
Why can't a similar argument hold for Taijuan Walker? If he had one peripheral stat that looked way out of line, I might buy the argument that he will regress to the mean with time. However, everything is out of line. There is something deeper going on.
I went into this post with a theory: Taijuan Walker is more of a thrower instead of a pitcher. In other words, he throws his fair share of strikes but often extremely hittable ones. I watched this happen in several Tacoma starts last year and he was too good to get touched up too often against AAA competition. Eventually it was bound to catch up to him in the majors.
Below are some color-coded tables. All of them are matrices that represent counts.
The left-hand ones show wOBA by count. The old adage that the best pitch is strike 1 is extremely true, and shows up in data. Hitters typically perform much worse when they are behind in the count and much better when they are ahead. The left-hand tables make a heat map of sorts to show what counts a pitcher is well above average in (those show up green) and well below average in (those show up red). A typical pitcher would have green zones in the bottom left corner, where counts they are way ahead in live, while exhibiting red zones in the top right corner, where hitters counts live.
The right-hand ones show how often Taijuan Walker faces a batter in each count. A typical pitcher will have a dark orange color in the top left corner that dissipates across the diagonal towards the bottom-right corner. This is because most pitchers throw a few more strikes than balls, and the average at-bat lasts 3 or 4 pitches. The extremes in the far reaches of the table require lots of pitches. The two tables together give a feel for what counts Walker typically works a batter to in an at-bat, and how batters fare in those counts:
Taijuan Walker, interesting enough, is NOT getting hit harder across the board in 2015. He got tattooed when he was behind the count in 2014, though like most effective pitchers he limited the opportunities that batters had to swing away ahead in the count. Overall, early in the season, Walker is roughly as ineffective when behind in the count.
It is worth noting that Walker's control has been shaky so far this season, which is born out in an elevated walk rate. It also shows up in the right-hand tables, which show darker colors in 2 and 3 ball counts this season. This starts to explain Walker's struggles. Batters are getting Walker in more advantageous hitting situations.
However, the real difference is when Walker gets ahead in the count. Last season he was quite stingy and flashed an ability to put away batters. This is what should happen when a pitcher has electric stuff. Once a batter is forced to expand the zone and chase, as with what happens when a pitcher gets ahead in the count, all that nasty swing-and-miss stuff translates to strikeouts and bad contact.
This year, at least so far, Walker is getting drilled when he is ahead in the count. In fact, one of the least effective counts for him so far is 0-2, which is insane. It would be easy to chalk this up to bad luck if only one specific count looked out of whack, but Walker is getting hit hard across the board.
The most likely culprit is Taijuan Walker's cutter. He is using it twice as often this season and has moved away from his curve ball. Cutters, even when they are super good, tend to generate weak contact instead of swings and misses. Walker is still pretty new to the cutter though, and if the results are any indication, his cutter is inconsistent at best. At worst it is a pitch that spins across the plate in the high 80s or low 90s, which is glorified batting practice for an MLB hitter.
Taijuan Walker is still a 22-year-old pitcher trying to find his identity in the major leagues. It's easy to forget that, given his tastes of success at the end of 2013 and 2014, plus his dominating performance in spring training. There are lots of predictable reasons that Walker is likely struggling right now though. For starters he is actively redefining his repertoire with his newfound emphasis on his cutter. This has a good chance to pay off down the road because it should theoretically be an easier pitch for him to command than his curve. Walker is also starting to face batters who have faced him in the past, and scouts have gotten several good looks at him against MLB competition. He has never in his past faced batters as prepared to face him.
The answer, long term, is not for Walker to go back to AAA. MLB hitters are illuminating holes in Walker's game that I am not convinced AAA batters would find. This isn't about something as simple as throwing strikes, and his stuff is good enough to overwhelm a number of AAA batters without really paying attention to command.
Taijuan Walker, despite being a top prospect on a team that expects to contend, is still developing and the Mariners would be wise to stick with him through the growing pains. He is not that far from being the kind of pitcher the M's can depend on for a run deep into October, and his odds of becoming that pitcher in the next few months are better if MLB-caliber hitters are pushing him to refine his craft.