Four days. It took MLB all of four days to bring us the first transaction of the off-season, as the Mariners and Rays got together on a six player trade that ships some interesting players in both directions. The full trade, as announced on Thursday evening.

Tampa Bay receives:

SS Brad Miller

1B Logan Morrison

RHP Danny Farquhar

Seattle receives:

RHP Nate Karns

OF Boog Powell

LHP C.J. Riefenhauser

While this is a six player deal, for simplicity, we can mostly break this down into three one-for-ones.

At the end of the deal, there’s a relief pitcher swap, with the teams exchanging a solid right-handed middle reliever coming off a down year for a left-handed bullpen prospect with good minor league numbers but poor big league performance in a couple of brief trials. Farquhar is a decent bet to be the more valuable of the two in 2016, but Riefenhauser could turn into a useful left-handed option down the line, and given the fungibility of relievers, this part appears to not be too dramatically tilted in one direction or the other, though I’d rather have Farquhar.

The middle part of the trade is a middling former first base prospect for a middling outfield prospect, with neither Morrison nor Powell looking to posses a ton of value. Morrison is a 28 year old first baseman with a career 105 wRC+, and one who is also a poor baserunner and doesn’t add much value with the glove. That adds up to something only a few ticks above replacement level, and with a projected $4 million paycheck coming via arbitration, Morrison was a potential non-tender candidate.

Powell is the kind of prospect that gets traded for non-tender candidates, an undersized outfielder who makes enough contact and draws walks to give himself a shot at a big league career, but with no power to speak of, the best case scenario here is Gregor Blanco, and even that’s unlikely. This part of the deal is mostly just moving pieces around, as neither Morrison nor Powell are likely to have a big impact on their new teams.

So, while this is a six player trade, it’s mostly a deal that involves Brad Miller getting traded for Nate Karns. The Mariners had more shortstops than they could play but not enough pitching; the Rays have more decent arms than just about anyone, but didn’t really have a shortstop. It’s a classic exchange where parties are moving from their depth, with both players likely being more useful to their new teams than they were their old ones.

As far the two primary pieces in the deal, your opinion about them can probably be summarized fairly easily based on how you answer a few questions. If I was better with MS Paint, I’d draw this up as a handy flow chart, but we’ll do a text-based one instead.

Do you put any stock in UZR as a reasonable defensive metric?

Yeah, sure; it’s not perfect, but with decent-sized samples, it points us in the right direction for most players.

If your answer is anything like the above sentence, then you probably think Brad Miller is a nice pickup for the Rays. Despite a recurring issue with making poor throws, UZR has Miller pegged as roughly an average defensive shortstop in a little over 2,200 innings at the position, or about two full years worth of games played there. If you think that’s in the range of reality, even if you think he’s more a little below average than average, then the rest of Miller’s game makes him a pretty solid overall player.

As a big leaguer, he has a 99 wRC+, which ranks 8th among players who have played at least 25% of their games at shortstop over the last three years. If you exclude Hanley Ramirez and Yunel Escobar — neither of whom played an inning at the position last year, and won’t play it in 2016 either — then you’re left with only Troy Tulowitzki, Jhonny Peralta, Jed Lowrie, Brandon Crawford, and Ian Desmond as shortstops who have better offensive numbers since Miller’s debut.

Given that he’s also a good baserunner and headed into the years where most players peak, there just aren’t a lot of guys out there who can play shortstop and provide this level of offense. League average hitting and above average baserunning while playing an up the middle position is a valuable combination of skills, and if you think Miller is a decent enough defender to hang around at shortstop for at least a few more years, then he profiles as a guy not too different from Desmond, who the FG crowd projected for a 4 year, $60 million contract this winter, and I had pegged a bit higher at 5/$85M. The offensive contributions for a shortstop are well above average, so if you buy into UZR’s assessment of his defense, the Rays just picked up a quality shortstop who will make something close to the league minimum this year. That’s a nice addition.

No, I don’t think UZR is a worthwhile measure of defense, and I don’t really care what it says.

If your answer is anything like the above sentence, then you probably don’t think Brad Miller is particularly interesting. Most scouting reports have been down on his defensive work since his college days, and his lack of physical tools kept him from ever being projected as a regular shortstop even as he hit well throughout the minors. The Mariners themselves questioned his abilities at the position, replacing him with Chris Taylor and Ketel Marte at different times over the last few years, and experimenting with him as an outfielder in the second half of last year.

So, if you buy into the idea that Miller is not an acceptable option as a Major League shortstop, and his defense limits him to being a second baseman who doesn’t add much value in the field, then he’s more like a left-handed Jedd Gyorko or Logan Forsythe, or a younger version of Luis Valbuena. These kinds of guys are nice role players and can even hold down regular jobs, but would-be contenders probably want to keep them in part-time roles, and they aren’t core pieces that you plan on building around.

If you see Miller as a 2B or 3B, or even an outfielder, then he’s probably not worth sticking in the line-up against a left-handed pitcher, as most teams are going to have a guy on the roster capable of playing one of those spots who can bat from the right side and offer a better option in a platoon. And Miller’s weakness against lefties means that you’re probably pinch-hitting for him in some late-game situations, so now you have a platoon infielder who doesn’t even play full games when he starts.

That version of Brad Miller is a decent piece, a guy who has some value on a roster, but nothing to get excited about. He’s a placeholder until you find something better. Your perception of his value hinges mostly on whether or not you’re comfortable with the idea that he can be an average or a little below average defender at shortstop for the next few years. Those who think the answer is no probably think the Rays got a big pile of meh in this deal.

Do you think that home run rates have much predictive value?

Yes, I think that pitchers who give up homers generally do so because they throw crappy pitches, and homer prone pitchers remain homer prone pitchers throughout their careers.

If you answered in the affirmative, you probably don’t think much of Nate Karns. In 171 big league innings, 15% of his fly balls have gone over the fence, so he’s allowed 1.42 homers per nine innings, the kind of gopheritis that makes it difficult to add value even if you control the strike zone well. Karns doesn’t have the kind of command that allows him to get away with also giving up home runs, so if the homer problem is permanent, he looks like a #5 starter, even with a decent strikeout rate.

And given that Karns has a long history of health problems — he ended up getting shutdown in September of this year due to the dreaded “forearm tightness” — and has never cracked 150 innings in a season, he might not even be the kind of durable #5 starter that you can count on to eat innings and save the bullpen. If you’re not going to prevent runs at a high rate, the other way to be useful is to soak up innings, but Karns medical red flags are one of the reasons the Nationals traded him to Tampa Bay to begin with, and he hasn’t yet proven that he can provide a high quantity of innings to offset some of his problems with the home run ball.

And while Karns’ strikeout numbers are nice, we have to adjust for the fact that the Rays utilized their starters for fewer innings than any other team in baseball, frequently removing them after they’d gone through the order two full times. In 24 starts, Karns only faced hitters 134 batters who were batting against him a third time through the order, and they .263/.343/.466 against him in those at-bats. So, beyond even his health issues, there’s questions about how effective Karns can be working more than five inning stints, and often times, pitchers with limited repertoires, health problems, and struggles as the game goes on get moved to the bullpen. If Karns home run problem persists, the rest of his flaws might suggest that his best path to a big league career is as a reliever.

No, I think HR/FB rates have too much variance to draw strong conclusions about them, especially with limited sample sizes.

If you don’t see home run rate as being all that predictive, then Karns might look like a pretty nifty buy-low opportunity for the Mariners. While his 115 FIP- is not very good, his 97 xFIP- (which normalizes his HR/FB ratio) is better than the league average, and puts him in the same group as guys like John Lackey, Jordan Zimmermann, and Wei-Yin Chen, all of whom are projected to get $15 to $20 million per year as free agents this winter.

Karns ability to miss bats as a starting pitcher makes him a valuable commodity, and strikeout rate remains the single best overall predictor of a pitcher’s future success rate. Guys who strikeout 23% of the batters they face are usually decent pitchers if they can throw strikes, and Karns throws enough strikes. Even if he’s more homer prone than an average pitcher, he’d still be an asset if his HR/FB rate settled in at around 11% to 12%; you don’t have to expect his HR/FB rate to regress entirely to the league average to see some upside here.

And free agent pitching is expensive. Mike Leake has an established homer problem that has sustained itself over 170 starts, and he’s looking at a long-term deal for between $50 and $100 million this winter, depending on whose estimates you look at. If the Mariners wanted to go out and acquire a starter whose BB/K/GB numbers were similar to Karns, they wouldn’t find many options for under $50 million. Given that Karns has just one year of Major League service, the Mariners now control his rights for five years, two of which are going to be at the league minimum. If Safeco helps him get his homer problem under control, and he stays healthy enough to take the mound a decent amount, Karns could prove to be a valuable middle-of-the-rotation starter.

Of course, breaking this trade down into simple yes/no questions about two particular skills of two players in a six player trade is a massive oversimplification of the deal, but by and large, your opinion of this swap is likely to be heavily influenced by what you think of Brad Miller’s defense and Nate Karns’ homer problem.

Personally, I think Miller’s mostly fine at shortstop, especially with a team like Tampa Bay that specializes in positioning their defenders, and my long-standing faith in his abilities remains. I think he’s the best player in this deal by a pretty good margin, and I think the Rays did really well to pick up a guy who can be an above average player during his prime years, which still lie ahead of him. I think Karns is interesting, and pitching is so hard to predict that it’s certainly possible that Karns turns out to be a quality starter for the Mariners, but there are a lot of red flags there, especially with regards to his durability, and if Safeco doesn’t fix the homer problem, then the Mariners might not have gotten much in this deal.

But every player in this trade has warts. It all depends on how much weight you put on different skills, and which flaws you think are fixable. For me, I’d rather have a middle infielder without elite defense and some problems against left-handed pitching than a pitcher with health problems and an issue keeping the ball in the ballpark, but with Ketel Marte and Chris Taylor still hanging around, the Mariners needed a pitcher more than they needed another shortstop. I just wouldn’t be too surprised if the Rays ended up not missing any of what they gave up, while Miller proves to be a pretty nice piece at a position that isn’t easy to fill.