A pretty common question we see in FanGraphs chats is what one statistic we’d use to evaluate pitchers, if we could use only one. The truthful answer is always a non-answer: You shouldn’t ever use just one statistic. It’s an unrealistic hypothetical, and good evaluation is done with a blend of different data. But I will say that I tend to look at xFIP early on, just to get a sense of what I’m dealing with. It’s a number that can scrape out a whole bunch of noise. Something I noticed is that, this season, Max Scherzer posted a 3.16 xFIP. Rick Porcello posted a 3.19 xFIP. Both were full-time starters for the same team, and one of them, presumably, is about to win the American League Cy Young Award.

It’s a comparison that’s interesting enough on its own, but adding more significance to the comparison is talk that the Tigers will explore trading one of these two pitchers in the weeks and months ahead. There’s skepticism everywhere that a team like the Tigers would actually think deeply about moving Scherzer, considering everything, but the ace is one year from free agency and he’s represented by Scott Boras. Porcello is two years from free agency, and the Tigers have Drew Smyly just about ready to resume starting. Really, the Tigers aren’t limited to picking one between Scherzer and Porcello, but things could well work out that way. And in talking about this, xFIP is only the start.

Let’s consider the pertinent information. By certain peripherals, Scherzer and Porcello are coming off similar seasons, at least on a per-inning basis. By runs allowed, Scherzer was much better, and that’s why he’s about to win a major award. Scherzer, again, has one year left, and he seems destined to test the market. Porcello has two years left, but he’s one of those Super Two guys. For 2014, both starters are arbitration-eligible, and MLB Trade Rumors projects Scherzer for $13.6 million and Porcello for $7.7 million. Those are going to function as our best salary estimates.

Right at the heart of this is trying to figure out the real difference, going forward, between Scherzer and Porcello. The xFIP numbers are meaningful, because they demonstrate the difference isn’t as massive as it is by name alone. Yet, Scherzer seems more able to work deeply into games. He made an improvement this past season by adding a curveball. Porcello, too, improved by adding a curveball, suddenly figuring out how to make batters miss. Porcello comes away looking a lot like Doug Fister, but one notes that Porcello’s ERA doesn’t match his peripherals. It seems like there could be more to this than just being a groundballer in front of the Tigers’ infield.

This past season, Porcello threw a lot more strikes with the bases empty than with runners on, with a much better strikeout rate and a much better walk rate. This is consistent with his career splits. Most pitchers are worse in from-the-stretch situations, but Porcello could be worse than average, his ability tilted toward pitching with no one on. His wOBA allowed with the bases not empty has been worse by 43 points. Scherzer’s has been better by 11 points. If this is capturing true talent, beyond just random noise, it could highlight a real difference, where Scherzer is more able to pitch effectively when a hit could be more damaging. Put a lot simpler: Scherzer could be better by more than a few hundredths of a point of xFIP.

How much better, is the important question. Steamer projects a 1-WAR difference. Last year there was more like a 3-WAR difference, and if you go by runs allowed, it was more like a 4-WAR difference. Seems to me like two might be reasonable, with arguments in either direction. Max Scherzer is better than Rick Porcello. Scherzer is not so much better than Porcello that attempting a comparison is a laughable waste of time.

If the Tigers are to trade either Scherzer or Porcello, dealing Scherzer might make them a couple wins worse. Conveniently, the difference between their projected 2014 salaries is roughly the market rate of one win, so that helps the trade-Scherzer case. That’s money the Tigers might elect to put toward second base, left field or the bullpen. Working in the other direction is that trading Scherzer now would presumably cost the Tigers a future draft pick, valued at some millions. Porcello is not nearly the same guarantee to end up receiving a qualifying offer and turning it down.

So the question becomes one of the expected difference in trade returns for Scherzer and Porcello. Scherzer would be marketed as an ace, as a Cy Young winner, while Porcello would be marketed as a durable sinker-baller with an extra year of admittedly expensive team control. Teams are smart enough to be aware of Porcello’s improvement. Teams also know Scherzer could be a very short-term addition.

We don’t have a long track record of good/great starters getting dealt with a year left. R.A. Dickey went to the Blue Jays with one year left, but he quickly signed an extension, and at the time he was an old knuckleballer with a $5 million salary. He brought the Mets back a great prospect and a good prospect. Anibal Sanchez went to the Tigers with a few months left, and he brought the Marlins back an interesting pitching prospect and a potentially useful catcher. Sanchez, however, was packaged with Omar Infante. Matt Garza went to the Rangers with a few months left, and he brought the Cubs back a frustrating high-level prospect and an interesting low-level prospect. Zack Greinke went to the Angels with a few months left, and he brought the Brewers back a good shortstop prospect who was just about big-league ready.

The Blue Jays intended to re-sign Dickey. The Tigers intended to re-sign Sanchez. The Angels, at the time, intended to re-sign Greinke. A team trading for Scherzer might intend to re-sign him, but that wouldn’t be guaranteed. It seems like he could bring back a package highlighted by at least one really good young player close to the majors, if not already there. That young player, probably, wouldn’t be a future superstar, since Scherzer does just have the one year left. The acquiring team would at least stand to pick up a draft pick after the season.

Meanwhile, Porcello likely wouldn’t bring back a top prospect, or an established young regular position player. He would have a big market, because he’s young and durable and possibly improving. But Porcello won’t be cheap the next two years and there’s reason to believe he’s not quite as good as his peripherals. Maybe Porcello would turn into bullpen help. Maybe he’d turn into a project, like a Dustin Ackley. Maybe he’d turn into intriguing low-level prospects with an eye toward re-stocking the system. Keep Porcello and the Tigers add more future value. Keep Scherzer and the Tigers preserve more current value.

That’s the real thing here. Scherzer is a dominant starter one year from free agency. As a target, he’d appeal to a competitive team with a shorter-term window. A team with a lot riding on trying to win it all in 2014. Maybe that team turns out to be the Nationals, but on paper, it sounds an awful lot like the Tigers. The Tigers are more interested in winning now than in winning in five years. With all of his strikeouts, Scherzer is a better fit for the team defense than Porcello, who allows more balls in play to the infield. Jose Iglesias can help, but he can’t cancel out Prince Fielder and Miguel Cabrera. Scherzer’s the win-now acquisition. The Tigers are a win-now team. It would be strange for them to make themselves worse.

The nuance is in the fact that it wouldn’t make them that much worse. We’re talking a win or two or maybe three, without knowing anything about the return. The salary difference between Scherzer and Porcello could be put toward a short-term improvement, and other moves could be made as well. Even trading Scherzer, the Tigers would remain World Series contenders, and they’d presumably be in better shape in the long run. It would be an interesting roll of the dice, and it could certainly be a reasonable one.

I just can’t really see it. I can’t see a team built for now unloading the Cy Young winner for youth. Not looking at another winnable AL Central. Maybe the Tigers could bring back a good young left fielder or a good young second baseman. Maybe the Tigers could make a move such that they’re not even worse in the short-term. But my guess is that the Tigers explore the Scherzer trade market and come away underwhelmed. They’re unlikely to fetch the blockbuster they might be seeking. And for that reason, I think Porcello’s the odd man out. Picking between Scherzer and Porcello is a fascinating question, but in this particular case I think it’s a question with a predictable answer.