St. Louis Cardinals free agent targets: Does Mark Buehrle have enough left in the tank?

On the surface, Mark Buehrle, a Saint Charles, Missouri, native, seems like a decent fit for the 2016 pitching staff of the St. Louis Cardinals. This notion was sparked by the report that Buehrle "will either retire or pitch for the St. Louis Cardinals in 2016." While it is a neat to think of the situation as truly "homecoming or nothing," Buehrle is almost certainly making such a public statement to provide his agent with leverage during potential contract discussions this offseason. Plus, while I am definitely a fan of "feel good" stories, should the Cardinals even be interested in providing a homecoming to Buehrle at this stage of his career (he turns 37 next spring)?

Buehrle is coming off a 2015 season in which he pitched 198.2 innings (coming up just short of his 15th straight 200 IP season), produced 2.1 fWAR, and earned $14.5 million (the last of a four year, $58 million deal). Those numbers are nothing to be ashamed of and would realistically slot into the #5 spot nicely of nearly any MLB rotation. However, after looking at some peripheral and PitchF/x data, one can reasonably wonder whether or not Buehrle would even be able to provide two-win value next season. First, let's take a look at his strikeout and walk rate over the last four seasons:

While Buehrle was never known for striking out a lot of hitters (his career high was 16.4% in 2000), his strikeout rate fell to a career low in 2015 at 11.0%, the lowest in all of baseball. Now, Buehrle is able to combat a low strikeout rate by walking virtually no one—his 4% walk rate was third best in baseball last season. With so few plate appearances being decided by strikeouts or walks, a considerable amount of Buehrle's success relies on the outcomes of batted balls.

Sure, pitchers have some control over batted balls (i.e. if you bust a hitter inside with a 95+ MPH fastball, you will likely induce weak contact), but as a given pitcher's repertoire weakens, he too experiences a decline in the ability to influence batted balls. Unfortunately, that's where we are with Buehrle and the state of his repertoire. Look no further than the following chart of his average fourseamer and sinker velocity since 2007:

via BrooksBaseball.net

Of course, Buehrle was never considered a "power pitcher" by any means, and he has proven capable of pitching with a diminished repertoire, but at some point, his performance will no longer be able to overcome such a decline in velocity. Fastball velocity matters in this instance, too, because Buehrle throws a combination of his fastballs 50% of the time, even last season. Oftentimes with a velocity decrease, pitchers benefit from subsequently having more horizontal movement on their pitches. This does not seem to be the case with Buehrle, as he had near career lows in fourseamer and sinker movement last season.

In closing, it would definitely help Buehrle's cause that he would be pitching in front of one of the league's better defenses (Please, sign Jason Heyward), but even the best defenses cannot prevent all batted ball luck, and all signs point toward even more batted balls against Buehrle. Some will point to a signing of Buehrle as a mere "depth" move, intended to ease the innings loads designated to Carlos Martinez (shoulder), Jaime Garcia, (plethora), and Michael Wacha (shoulder). Yet, even as depth, I am not convinced 2016 Buehrle exceeds the value of 2016 Tim Cooney or Marco Gonzales, who will both be pitching at the league minimum.

If John Mozeliak and the Cardinals truly feel the need to add a pitcher in 2016, I am all for it (as long as they also sign Heyward), but I am not sure Buehrle is a viable option, even if he accepts a low base, incentive-laden deal.