Should the St. Louis Cardinals sign reliever Pat Neshek to a contract extension?

St. Louis Cardinals righthanded reliever Pat Neshek made his 51st appearance in relief for the club on Wednesday night against the Red Sox. The sidewinder slung 13 pitches while recording three outs—all of which via the K. It was a dominating performance, after which Neshek expressed his interest in signing an extension with the Redbirds. Per ace St. Louis Post-Dispatch reporter Derrick Goold:

"I like it here," said Neshek, a free agent at the end of the season. "I like how I’m being used. That’s a big part of it. That’s the feeling I have. That’s one of the main things. I feel like I pitch really well at Busch Stadium. I think that would be good for my career, right? I just really like it here."

Neshek is certainly negotiating from a position of strength. The righty has been lights out for the Cardinals this year.

Pat Neshek 2014

Neshek has pitched extremely well over 46 1/3 innings for the Cardinals so far this season, posting a 0.78 ERA that is rather shiny and completely unsustainable. Opposing batters will experience better luck on balls in play, raising Neshek's BABIP. Some of that luck will occur with ducks on the pond, and Neshek's LOB% will drop closer to the typical league-average rate of around 72%. The corresponding effect will be a higher ERA. Whether it occurs in 2014 or beyond, Neshek is going to allow runs at a higher rate in the future.

But is the fact that Neshek will allow more runs going forward a big enough deal to refrain from extending him?

The Butler alumnus is striking batters out at a near-30% clip while issuing walks just 3.6% of the time. That's terrific. And his FIP shows it. Based solely on Neshek's 2014 performance, his 0.78 ERA is unsustainable, but FIP suggests he has pitched well enough for an ERA in the low-2.00 range. Factor in Neshek's low homer rate—a type of hit that Busch Stadium suppresses—and his ERA ought to be in the low 3.00's according to xFIP.

Looking at Neshek in the vacuum of 2014 tells us that he has not pitched as well as his sterling ERA suggests, but that he has still been quite good. However, 2014 is just one data point on Neshek. And the 33-year-old's 46 1/3 innings of work this year are head and shoulders above what he has done over the course of his career.

Perhaps working with the Cardinals coaching staff has helped Neshek develop as a pitcher—namely, by issuing fewer free passes and inducing more strikeouts. If not, then he's a pitcher with a large ERA-FIP gap that seems unlikely to continue. Bear in mind that Neshek has played nearly eight MLB seasons and, because he is a reliever, he has only notched about as many innings from 2006 through Wednesday night (and excluding 2009) as Adam Wainwright threw last year between the regular season and playoffs. If Neshek's career as a reliever consists of roughly the same amount of innings pitched as a workhorse starter who led the league innings. And if we look at Neshek's stats through that prism, we see a pitcher who is likely to allow more runs going forward. And so much so that his performance would sink to replacement level or below.

The low innings-pitched totals that relievers put up leaves their performance from season to season subject to much higher volatility that their starting counterparts (or positions players' batting, for that matter). This makes their future performance nearly impossible to project. After all, who would have predicted Neshek would have a 0.78 ERA on August 7, 2014 when pitchers and catchers reported for spring training? I doubt even our own Joe, a Butler Bulldog and big Neshek fan, would have predicted such a great season. It seems just as likely that Neshek will post a 4.00 ERA in 2015 that is close to his career FIP as a 2.00 ERA close to his 2014 FIP. Such is the nature of relief pitchers.

So the question general manager John Mozeliak is now faced with is a tricky one: Should the Cardinals bet on Neshek's career year with a contract extension? I'm not so sure they should.