The Yankees need to keep David Robertson around to in order to strengthen the bullpen as a whole
2014 Statistics: 3.08 ERA, 2.68 FIP, 13.43 K/9, 3.22 BB/9, 39 SV, 64.1 IP
2015 Age: 30
Position: Closer
Conventional baseball wisdom says that relievers are mostly fungible and you shouldn't devote money and years to them when you don't have to. However, if you've been paying attention to the playoffs at all, it's clear that the best teams have the best bullpens. We've seen the Royals thrive with one and the Tigers suffer without one, and while the Yankees bullpen has been really good in recent years, it's going to take a hit in the offseason when David Robertson, one of the best relievers in baseball, becomes a free agent.
We all know what Robertson can do. The argument to re-sign Robertson really revolves around Dellin Betances. Many have said he should be crowned the new closer and Robertson should be allowed to leave so the Yankees can use the money elsewhere. That's certainly a legitimate way to build a bullpen, but if the Yankees want a truly elite backend, they should be looking to keep their closer around for the foreseeable future. While Dellin would likely make for a great closer, the Yankees are better off with both of them. Just like Mariano Rivera and David Robertson were an effective one-two punch, Robertson and Betances would offer a real combo at the backend of the bullpen, one they would not have if Robertson was allowed to leave.
The Yankees could easily fill Robertson's role with Dellin, but the real problem would be replacing Betances. Moving him into the closer role would cement him into the ninth inning and severely damage his value as a multi-inning reliever. The rest of the Yankees bullpen is filled with interchangeable parts that shouldn't be trusted in high-leverage situations on a regular basis, so by keeping Betances/Robertson intact, we don't have to see Shawn Kelley as the primary setup man.
Sure, the farm system has plenty of top talent coming through the pipeline, but even if Jacob Lindgren, Nick Rumbelow, and Tyler Webb all end up as important major league relievers in 2015, you can't go into the season expecting it. They'll start off with easy innings until they prove they can handle the challenge. If they pass, it would make the games so much shorter and mean the Yankees would still be better off with Robertson as the closer.
While longterm contracts are tricky with relievers, at least you know what you're getting by signing Robertson. They might not receive a hometown discount, but they'll be more comfortable giving out a bigger deal to someone who is already familiar over someone completely new like, say, Andrew Miller. Giving out big contracts to relievers still isn't the wisest of baseball moves, but in today's run environment it might be a necessary evil. With the rise in reliever value, David Robertson will be looking to cash in this offseason and the Yankees need to work something out quickly before they get into a bidding war that makes a deal impossible. There might come a day when Robertson can no longer do the job, but right now he's only 30 and he still should be effective for at least several more years. He's someone that the Yankees shouldn't be afraid to pay (a little) extra to keep around.