When posed with the question, "who was the best catcher in 2013?", most people would be stuck between two names: Yadier Molina and Buster Posey. After last season's stellar performance by Molina -- he finished in 3rd in the NL MVP voting with 219 points -- and Posey's brilliance at the plate, it's hard not to point to those guys.

But, there was one catcher last season who was remarkably close to both Molina and Posey, despite his near-Mendoza line .226 batting average. His name is Russell Martin, and he's a large -- and mostly secret -- reason why the Pittsburgh Pirates made the playoffs for the first time since 1992.

What value Martin did have at the plate only appeared in the beginning of his career. He posted a wRC+ of over 104 twice in his career, both in his early days as a member of the Los Angeles Dodgers, and a wOBA of over .340 three times, also in his first three seasons in the league. In recent years, though, he's become little more than a slightly less than average hitter, posting wRC+ totals 100, 95, and 101 in his past three seasons, the first two with the New York Yankees and the last with the Pirates.

Whereas Molina and Posey have the more marketable skills -- hitting for average and power, especially on highly viewed teams like the St. Louis Cardinals and San Francisco Giants, respectively, tends to garner a lot of attention -- Martin is still nearly as valuable as a player based on defense alone.

First, let's look at their batting numbers, setting aside defense for a minute:

Player PA BB% K% ISO BABIP AVG wOBA wRC+ Yadier Molina 541 5.5% 10.2% .158 .338 .319 .362 134 Buster Posey 595 10.1% 11.8% .156 .312 .294 .357 133 Russell Martin 506 11.5% 21.3% .151 .266 .226 .315 101

Martin falls behind in almost every category save for BB%. Even with a pretty good batter's eye, it's not enough of a difference to overcome his deficiencies in nearly all other offensive categories. Instead, Martin's value derives almost solely from his unmistakable defensive prowess behind the plate. And, as a result, his value as a player is nearly equal to that of both Molina and Posey:

Player RAR fWAR Dollars Yadier Molina 52.0 5.6 $28.1 Buster Posey 44.1 4.8 $23.8 Russell Martin 38.0 4.1 $20.5

See? A lot closer in value than their offensive numbers would have you believe. That's because Martin wasn't just seasonally great defensively at catcher in 2013; he was historically great. Since 2002, these are the five best defensive seasons, as judged by the fielding component in fWAR, for catchers:

Player Year Def Russell Martin 2013 22.5 Yadier Molina 2010 21.9 Jason Kendall 2008 21.7 Matt Wieters 2011 21.2 Brian McCann 2010 20.7

Martin had the best defensive season as a catcher in over a decade. Taking a glance beyond the all-encompassing Def statistic, though, will lead you to Martin's uncanny ability to block the plate, which was on full display in 2013. Since 2002, here are the ten best single seasons in Calculated Passed Pitches (CPP):

Player Year CPP Brian McCann 2011 70 Russell Martin 2013 65 Jason Kendall 2009 63 Yadier Molina 2011 62 Brian McCann 2010 61 Jonathan Lucroy 2011 59 Russell Martin 2008 58 Russell Martin 2011 56 Yadier Molina 2009 56 Jason Kendall 2010 56

As you can see, Martin has led the league in CPP twice in the past six years, in 2008 and 2013, ranked fourth in 2011, and he's the only player in the top ten to appear three times.

But, going back to 2013, how much better defensively was Martin than his National League counterparts in St. Louis and San Francisco? Well, to be frank: a lot. Here's how his defensive stats compare with Molina and Posey's:

Player rSB DRS CPP RPP Def Yadier Molina 2 12 42 5.9 17.5 Buster Posey -1 4 41 2.5 10.4 Russell Martin 9 16 65 4.5 22.5

With the exception of Passed Pitch Runs (RPP), which looks at how a catcher ranks in terms of blocking pitches, with 0 being average and +5 being excellent, Martin dominates in almost every category. Even including RPP, Martin's impressive 4.5 ranks him second in the MLB, behind only Molina.

Martin was an integral part of the Pirates' success in 2013. Still, considering everything -- Martin's seemingly paltry offensive numbers compared to both Molina and Posey, juxtaposed with his elite defense at one of the most important positions in baseball -- it's hard to conceptualize just how important Martin was to his team.

Although Martin's 4.1 fWAR was a far cry from NL MVP Andrew McCutchen's 8.2, it still ranked him third on the team, just behind the speedy centerfielder Starling Marte, who posted a 4.6. Remember, that's better than Pedro Alvarez, who smashed 36 home runs with a .473 SLG% and 111 wRC+; A.J. Burnett, who posted nearly 200 innings of 76 FIP- ball; and Francisco Liriano, who had a team-leading 16 wins with an 80 FIP- over the span of just over 160 innings.

At this point, it's clear that statisticians are finding it difficult to quantify the defensive value of a catcher. Maybe it will always be difficult to quantify one of the most cerebral parts of the game. But, one thing is for sure: Russell Martin is one of the best catchers in the game, and he has put himself in that conversation almost entirely with his glove.

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All statistics courtesy of FanGraphs

Evan Kendall is a contributor at Beyond the Box Score and co-founder of The Sports Post. You can follow him on Twitter at @Evan_TSP.