Try to Tell the Difference Between Jake Arrieta and Tanner Roark
I have to admit to a bias. I’ve been aware of Tanner Roark since he entered the major leagues a few years ago, but my evaluation failed to evolve. In my head, Roark was still the guy he was when he made his first impression, as a strike-throwing and hittable sort who seemed to pitch with the intent of beating his peripherals. It is my job to try to know as much as I can, and I concede that this is my own failing, but in my partial defense, Roark hasn’t been close to the most interesting member of the Nationals’ pitching staff. Why would I choose to concentrate on Roark, when I could focus instead on Max Scherzer or Stephen Strasburg?
I have to admit to another bias. I find it tempting to believe that the larger population perceives things in the same way that I do. I haven’t kept up with Roark; therefore, I bet no one has kept up with Roark. Sometimes this gut feeling is correct. Sometimes, I’m just out of the loop. In any case, I’m about to put you all to the test. This isn’t going to be about me anymore.
The Cubs and Nationals are scheduled to begin Game 4 of their NLDS in a little while. It looks like some ugly weather could blow in, so maybe the game won’t be played, and maybe the starters will change. But for now, according to the lineups, Tanner Roark will start for the Nationals, and Jake Arrieta will start for the Cubs. Feels like an advantage for the Cubs, doesn’t it? Doesn’t it? Doesn’t it?
It can be hard to shake old impressions. Roark seemed to be mostly unremarkable. While that was happening, Arrieta was establishing himself as arguably the best starting pitcher on the planet. I think we all understand Arrieta’s now somewhat diminished, yet he was what he was, and that wasn’t so long ago. In an effort to be quicker to the point, I have prepared a 16-question quiz. Every question concerns 2017 statistics, put up as a starter. You are to select which pitcher you think put up the stat in question. Don’t worry if you get something wrong — there won’t be a follow-up. Getting something wrong is the whole point. You know how this works.
Arrieta is a 31-year-old righty who just made 30 starts. Roark is a 31-year-old righty who just made 30 starts. How well can you tell them apart, by their performances? Let’s see.
ERA
FIP
xFIP
wOBA against
K-BB% (HBP included)
GB%
HR/FB%
Hard-Hit%
Strike%
1st-Strike%
Contact%
O-Swing%
Fastball MPH
Three-pitch strikeouts
Four-pitch walks
Innings/Start
If you’re someone who actually made it all the way through the quiz, you’d probably like an answer key. How frustrating would it be to not know the answers? I’m not going to put the answers in this actual post, just because I don’t want to bias any voting, but here’s a link to a full table of numbers. The hyperlink provides a one-step barrier between the questions and the solutions. So, go ahead, click through, if you’re all done. There’s exactly one area where there’s a meaningful difference between the two pitchers. Granted, it’s an important area, but the stat itself is volatile, and Roark has excelled in that category in the past. Maybe I’m not reading the room correctly, I don’t know, but as I put this together, I couldn’t believe it. I couldn’t believe the similarities, because I’m guided by the perceptions that I have in my head, and my perceptions can sometimes be off.
I did figure that maybe Roark just faced worse competition. After all, the rest of the NL East this season was bad. But then, there are helpful numbers from Baseball Prospectus. Roark’s average opponent batted .253. Arrieta, .249. Roark’s average opponent had an OBP of .319. Arrieta, .320. Roark’s average opponent slugged .414. Arrieta, .416. Nothing there. Nothing…really…anywhere. If there’s a difference, it’s a difference in ceiling, but even that isn’t a thing that really exists in a knowable sense. Arrieta used to be as good as anyone else. Why should we care about that now, if the performance no longer matches up?
No need to go any further. I, at least, have learned something today. I didn’t expect to learn it, but then, that’s the fun of statistics.
Jeff made Lookout Landing a thing, but he does not still write there about the Mariners. He does write here, sometimes about the Mariners, but usually not.
Baseball reference likes one of the players much, much better.
That comes down to runs allowed, which is captured by the ERA in this article. But is there any reason to believe, from this moment on, that will continue? Nothing in the stats, at least.
If you look at their entire careers rather than just the previous 6 months, yes, there’s a reason to believe Arrieta will continue to post a much better ERA.
Last question of the quiz. Which career ERA belongs to which pitcher? Pitcher A:3.57; Pitcher B:3.41.
Yeah, but who cares what they think?
(I was going to post a longer comment but that was gonna be the main takeaway either way)
The FG projection agrees with this. The series win %s started at 50/50 suggesting the batting is projected to be about the same. That remains true for today’s series projections with the Nats being given a 25% chance of winning. But today’s game, with Roark in as the starter, has Cubs 59%, Nats 41% chance of winning.
Actually, as of right now, on the score page, Roark is starting and Strasburg is batting 9th. I assume we’ll get new projections once that is fixed. But, they won’t be relevant to this article.
This doesn’t surprise me alot. Jake has had some really rough stretches since end of last year going into this year. One note, he has run good BABIPs for four years in a row. Some of that is the Cubs defense, but he is also a ground ball pitcher. So slight edge to Jake maybe.
Roark is also a ground ball pitcher, though. Arrieta’s career GB% is a little higher, but Roark’s 2017 GB% is a little higher. Both in the high 40s.
The big takeaway for me from that table isn’t just that they’re very similar in their results — they’re also very similar in how they produce their results. Almost all of the stats mentioned in this article, including the peripheral ones, are very close to each other.
Having not followed either player very closely this year, I must say I actually thought of Roark as better than Arrieta.
This might be on me!
Specifically, I remember Roark’s 2014, when he was fantastic in the rotation and then got inexplicably bumped to the bullpen. He returned to the rotation in ’16 and once again was great, better than both Scherzer and Strasburg on a run-prevention basis in fact.
The only year that Arrieta has ever had a clear advantage over Roark was 2015, the year that Roark pitched out of the bullpen. Arrieta may have been as good as anyone else, but so has Roark at the same time.
Well, Arrieta’s 2015 was a pretty dang big year. I have a lot of respect for Roark, and I don’t really know what Jake’s true measure is right now. But if you just sum any combo of each guy’s seasons within the last 4, it’s Arrieta all the way.
I feel like last year, baseball broadcasts were full of trivia questions like “Which Nationals pitcher has been the best at … in 2016?” and the answer was always Tanner Roark. Maybe I just caught this in a disproportionate number of broadcasts, or maybe I’m misremembering how often this happened, but it seems to me that Roark was getting some love from many directions.
(Now a minute after having commented, though, I realize I might have misinterpreted what you meant by your comment that I replied to)
On a tangent … If you knew that Arrieta had:
— 4.36 ERA in one half of his starts;
— 2.69 ERA in the other;
— 12.7% SO-BB in one half; and
— 17.8% SO-BB in the other;
you’d assume the much better SO-BB went with the better ERA.
But you’d be wrong. In Arrieta’s “improved” second half, both his SO and BB rates got notably worse. He trimmed a few HRs, and his BAbip plunged 64 points (with a far wider gap in the RISP spots).
Roark also improved in his second half, but that was consistent with better SO-BB, up from 11.2% to 15.3%. But, his BAbip also plunged 49 points.
So, who are they right now, really? Beats me. That’s why they play the games!
Which pitcher’s velocity has been been in freefall for the past month?
The “finding” of the article appears to be that Arrieta and Roark were very similar in 2017. But, while technically true when viewed as a whole, Arrieta himself had two rather dissimilar halves to the season, so I’m not sure how this comparison provides any insight about the two of them going forward.
Arrieta had a half with a higher ERA and a half with a lower ERA. That was the only difference.
2 runs of ERA is pretty big difference, though.
Arrieta had actually been struggling with blister issues for most of the first half and a little bit into the second half:
http://www.chicagotribune.com/sports/baseball/cubs/ct-cubs-jake-arrieta-20170715-story.html
He was the pitcher of the month in September (whatever that’s worth) and he seemed to be getting back into form before the hamstring injury. If there were splits from since his blisters ended (whenever that was), that might be the best indicator.