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Nate Karns into the bullpen

Anything can happen in the bullpen.

Troy Taormina-USA TODAY Sports

Let’s assume for a minute that the Rays know what they’re doing with Matt Moore. Let us assume that the ridiculous strikeout numbers he’s put up during his latest rehab stint in Durham—the ones that might remind you of "Once-In-A-Generation-Prospect Matt Moore"—are indicative of where he is as a pitcher right now and that Kevin Cash and Jim Hickey would be crazy not to slot him back into the rotation.

Even if all that is true, there’s still an interesting dimension to the decision to give Matt Moore a starting spot but to NOT go to a six man rotation. That means that Nathan Karns, who has been a pretty good starting pitcher this season, will be moving to the bullpen for the final month.

What does this mean for Karns? What does this mean for the Rays?

Starting is Harder than Relieving

The first point to make is that being a starting pitcher is hard. You have to save your strength and play the long game. Hitters have game-planned for you. They get to see you multiple times. They will adjust.

In the bullpen, though, everything you do is fresh and surprising. You can throw your heart out because you know how long your appearance will be before you start. You can concentrate on just a couple of your best pitches rather than mixing in all of your offerings to keep hitters off balance. Wade Davis was a talented pitcher who was failing as a starter, but the move to the ‘pen made him among the most dominant arms into the league. Ditto, to a lesser extent, JP Howell. Ditto, we hope, with Alex Colome.

There’s no guarantee that Karns will transition to the bullpen smoothly, because not everyone does so immediately (Alex Colome didn't; more on that later), but if he can figure out how to stay physically and mentally ready in a new role, there are dominant relief innings waiting for him.

More Pitchers are Better (as long as they aren’t all starters)

If there’s one concept that has come to define this season for new manager Kevin Cash and the Rays, it’s been the early hook. The argument goes like this:

  1. As hitters see a pitcher’s stuff multiple times through the order, they start to adjust. There’s a major jump in hitter success when the lineup turns over for the third time through.
  2. To best prevent runs, teams should weigh the expected performance of their starter against the hitters he’s set to face against the expected performance of the available bullpen. The result of this decision making process can often result in pulling a pitcher before he’s shown signs of tiring, and before the normal convention would dictate.

Of course, following this strategy has its downsides. It flies in the face of baseball tradition, for one, and that can make people uncomfortable. More importantly, it shifts an unusual amount of work onto the bullpen, and while it’s difficult to quantify the effect of that extra work, I think it’s safe to assume that there is one.

September callups solve some of these issues but not all of them. The Rays are able to bring up enough pitchers to prevent overwork, but there’s still that pesky little issue of quality.*

*For instance, last night Kevin Cash went to Matt Andriese in the tenth inning to face lefty Chris Davis, despite having lefties Enny Romero and CJ Riefenhauser available (Xavier Cedeno was also available, but probably being saved for a more lefty-heavy possible eleventh). That ended poorly for Andriese and the Rays, but hindsight is 20-20. The point is that a full bullpen isn't necessarily the same thing as a bullpen a manger is happy to use.

When the starting pitcher is Chris Archer, it probably doesn’t make sense to pull him early. He’s better when facing a batter for the third or fourth time than most relievers are against that batter for their first. This is the same reason that going to a six-man rotation wouldn’t make much sense. The goal should be to have Archer throw more of the important innings in this stretch run, not fewer.

And pulling Erasmo Ramirez from a game in the sixth inning might make sense when the Rays are set to mix and match Brandon Gomes against a righty, Xavier Cedeno against a lefty, and then trot out Kevin Jepson (RIP), Jake McGee, and Brad Boxberger in order for the final three frames, but it stops making sense when it means that the next day Cash has to turn to Kirby Yates (and his amazing ability to give up home runs) with the game on the line.

But adding Moore to the starting rotation and moving Karns into relief hypothetically kills two birds with one stone. It might or it might not make the starting rotation better, but it definitely beefs up the bullpen’s ability to cover innings and therefore means that the starters will be asked to do even less.

If Nathan Kearns and Alex Colome can soak up important innings two or three at a time, then the downside to pulling Ramirez or Moore early stops being an issue.

Matt Moore’s Caddy

There’s a concept that we always seem to talk about in September, which is that of one starting pitcher being a "caddy" for another. The idea that Matt Moore could pitch three innings and then give way to Nathan Karns for three innings sounds snazzy, because it would allow both of them to pitch to the top of their ability, and would prevent an opposing manager from stacking his lineup against opposite-handed batters for either one of them (Moore being a lefty and Karns a righty).

The "caddy" arrangement never seems to quite shake out in real life, though, and I don’t think it will this time either. The first, and most surprising (for me at least) reason, is Nate Karns’s splits.

Think about Karns for a minute. How do you expect him to perform when facing a righty? When facing a lefty? You’ve either been paying really good attention or you're wrong.

vs. RHP vs. LHP
IP 83.2 84.1
wOBA 0.314 0.319
K% 20.2% 25.5%
BB% 5.6% 12.2%
FIP 5.17 3.79
xFIP 4.08 3.78

Those are career stats, but they're mostly influenced by this season.

I bet you thought Karns has been better against righties than he's been against lefties. But depending on which stats you like to look at, he's either had neutral splits or he's been more effective against lefties than against righties.

That's not so surprising for a pitcher whose secondary pitches are a transcendent curve and a developing but good useful changeup, as both of those pitch types work well against opposite-handed hitters, but it is unusual in the grand scheme of major league pitchers.

What it means is that Kevin Cash probably shouldn't worry too much about getting Karns in to face the lineup of righties sent against Matt Moore, and should just pitch him whenever and against whomever he's needed.

The First Inning

There's another split that's gotten more attention this year with Karns than the lefty-righty numbers. This season, Nathan Karns has stuggled in the first inning. Opposing batters have hit .292/.369/.492 against him in the first inning, for a 6.97 ERA. That's far worse than his overall numbers, which are .239/.315/.407, and a 4.02 ERA.

We don't know how much of those numbers are a truthful representation of his talent, and how much of it is just rotten luck, but it's fair to suggest that there might be something there. Maybe Karns is having trouble getting warmed up well enough to start the game, and then he settles in after a bit of live throwing?

This is knowable only to Karns and the Rays training and coaching staff, and I'm sure they're working on it, but it does make a move to the bullpen interesting.

Some time ago I had an email correspondence with Alex Colome's agent, wherein Colome explained, through the agent, that in previous years he'd had difficulty getting completely warm while working out of the 'pen, and that this lead to him giving up some crooked numbers when he first entered the game. After a stint in the rotation, and a move back to the bullpen, it's pretty clear that Colome has figured himself out. His recent relief work has been of very high quality.

I tell this story to make a few points:

  1. Familiarity with one's role can matter.
  2. Players can evolve. Past failure in a situation doesn't mean a player will always fail in that situation.
  3. It's hard to know what will be the fix.

Maybe changing Karns's routine will blow up on the Rays he'll walk three batters and then give up a home run every time he enters the game in the fifth inning. Or maybe changing Karns's routine now will help him become a better starting pitcher in the future.


I'd be lying if I tried to say that I knew moving Nathan Karns to the bullpen and filling his spot with Matt Moore was a good idea. If Matt Moore is able to pitch at a high level, though, freeing Karns to work in relief has the potential to allow Kevin Cash to use his bullpen like every game is a must win, which is convenient, because that's the situation the Rays increasingly find themselves in.

There's risk in asking a pitcher to work differently than he has in the past, and there may be more risk with Karns than with some other pitchers, but the short-term reward is clear, and there may be a long-term reward as well.