If you consider his performance over the past few seasons as a whole, it’s clear why the Nationals gave reliever Brandon Kintzler at least $10 million over the next two years to pitch in Washington. Isolating just his 2017 campaign, however, there’s reason to think there’s some risk attached to the deal despite the modest price tag.

Since the beginning of 2016, Kintzler has used his sinker to induce ground ball after ground ball. Indeed, only 13 qualified relievers have recorded better ground-ball rates over those two years. Only 31 sinkers, meanwhile, have allowed a lower launch angle (minimum 150 balls in play). It’s largely that pitch which has allowed Kintzler to suppress homers despite having exhibited little capacity to miss bats.

In a world where Anthony Swarzak and his lack of a track record is getting two years and $14 million, this deal makes absolute sense. If a club’s player-value metric says the reliever class of player is consistently overpaid, there are only two choices: either (a) never pay a free-agent reliever or (b) try to get value from one of the cheaper ones. In that regard, the Nationals did well.

On the other hand, there’s this:

That, as you can see, is a graph plotting the average launch angle allowed by Kintzler over the last few years. The trend is distinctly upwards.

Maybe it’s just hard to keep being as good as Kintzler was in 2016. If you look at the rest of the bottom 20 in launch angle off the sinker that year, you see a fair amount of injury and fallback in the group. Bill James once famously thought that the hard sinker was linked to injury, which seems notable even if attempts to replicate his findings were unsuccessful. It is worth mentioning that Jeff Zimmerman and I looked at aging curves for ground-ball pitchers and found a whiff of unsustainability about that approach.

Kintzler, on average, lost about an inch of drop on his sinker between 2016 and 2017.

Is it just a matter of finding that drop again? Is Kintzler worth the modest deal even if his launch angle, ground-ball rates, and sinker are more top 50 than top 20? Maybe. But for the Nationals to go toe to toe with the bullpens they’ll see next fall, they’ll have to hope they bought more of the early version than the later one.