Why you don’t make Dellin Betances a closer.

Dellin Betances is having a phenomenal season. By fWAR, Betances ranks first among relievers at 3.2. His K/9 (13.5) ranks sixth, his ERA (1.33) fifth.

But here is where Betances really separates himself: His 88 IP are the most in baseball. That’s nearly 20 more innings than the next-highest total among top 20 fWAR relievers. That gap is monstrous.

Betances just broke Mariano Rivera’€™s single-season relief strikeout record this week. More impressive was that he did it in 20 fewer innings than Mo, who set the record as John Wetteland’s setup man that year. The feat has prompted the question: Should the Yankees let impending free-agent closer David Robertson walk, and anoint Betances the new stopper?

No.

Betances will have just over one year of service time after this season, which means the Yankees can control his salary reasonably well for the next five years. But it’€™s not about the money. It never is with the Yankees. This is about maintaining a better bullpen.

Brian Cashman and Joe Girardi are smart. They know Dellin Betances has more value to their team as a setup man as opposed to a closer. Just like Wade Davis (2.9 fWAR) is more valuable to the Royals than Greg Holland (2.1).

Even most casual baseball fans have learned that saves are just bright shiny objects, a highly overvalued stat. We’€™re in awe of the big totals but we also know it’s the setup man who gets more tough outs late in games. (You did know that, right?)

Dellin Betances is the best reliever in baseball in 2014, and we can reasonably expect him to be pretty good for a while. When you have a great asset, you should use it. As a setup man, Betances generally pitches whenever it’s close. As a closer? Up by three or fewer, almost exclusively in save situations and rarely in tie games, especially on the road.

The Yankees have a good thing going. Robertson is just 29 years old, Betances 26. This dynamic duo with the highest K/9 combination of any relievers in MLB needs to stay together. But even if the Yankees can’t re-sign Robertson, get another closer. Betances is worth too much as a setup man.

Let him become a closer when he hits his early 30s. Then another team will overpay him. There’s one born every day.