Why is Tyler Clippard still a free agent?

The 2015 off-season has been notable for a variety of reasons, from the creative use of opt-outs and contract structure to the relatively late developing market for free agent position players. One particular emerging trend has been the seemingly steep price paid for high-leverage relievers.

Beginning with the Red Sox's surprising acquisition of Craig Kimbrel, through the Astros' trade for Ken Giles, and the Dodgers' abandoned trade for Aroldis Chapman, elite level closers have flown through the trade market for large returns. Even in free agency, less high-profile players like Ryan Madson, Tony Sipp, Shawn Kelley, Joakim Soria, and Darren O'Day have each signed deals at least three years in length.

Competitive teams appear to be reevaluating relief pitching, so it initially struck me as odd that a pitcher of Tyler Clippard's track record, relative youth, and recent results remained a free agent this late in the off-season.

He produced a 2.92 ERA over 71.0 innings pitched in 2015, and was good for 1.1 WARP, according to Baseball Prospectus' DRA-based metric. The latter figure places his 2015 season 53rd among relievers, roughly in line with other late-inning types like Jonathan Papelbon and Will Smith.

To begin addressing the question of why teams aren't clamoring to sign him in this heightened environment for relievers, first understand why he's been so good for several years. This profile by Eno Sarris describes the mechanics-driven relationship between Clippard's high fastball and exceptional changeup.

Clippard's height-adjusted release point is in the top 15 percent of the league, and so he was maybe destined to throw a rising fastball. ... Clippard uses a four-seam grip on the changeup so that it comes out looking the same as his fastball. He even throws it high in the zone sometimes -- despite your average pitcher's aversion to "hanging" changeups -- with the idea that it's supposed to look just like his fastball.

Clippard has a history of good strikeout numbers, but an important by-product of this focus on rising movement is a consistently high pop-up rate, as batters get too far underneath his two primary pitches. Clippard's 15.2 percent infield fly rate ranks highest among all relievers with at least 300 innings pitched from 2009-2015 (the season he began relieving).

However, this skill's predictable counterbalance is a low 27.3 percent groundball rate, the lowest among the same sample. In 2015, this was a particularly low 21.2 percent rate, while his 21.3 percent strikeout rate was a significant drop from his career 27.7 percent rate as a reliever.

While his change-up remained pretty consistent after his July trade to the Mets, his fastball faltered in potentially concerning ways. Most immediately, he lost almost a mile per hour in velocity somewhere between the two halves of the season (from 92.8 MPH to 91.9 MPH). He additionally dropped his vertical release point on both the fastball and changeup (the pitches featuring the same four-seam grip) during September and October, when he most struggled.

I'm certainly not qualified to proclaim a pitcher injured, but the abrupt, mid-season velocity decrease and lowered release point (a factor that has been statistically correlated to injury) are reasons for concern. These components compromise Clippard's trademark "rising" action on his fastball, and threaten the changeup that thrives off its similarity to the pitch.

Especially with pitchers who have been used as much as Tyler Clippard , a natural break down in velocity is expected after several seasons of his degree of usage. Since 2009, he has thrown 524.2 innings - by far the most of any reliever, and 44.1 innings more than the second place pitcher (Luke Gregerson).

While yes, he debuted in the majors as a starting pitcher, and has the body for a heavier workload, his lack of total rest could be significant. Baseball-Reference's Play Index lists Clippard among the top five pitchers used on either one or no days rest, since converting to relief.

He's pitched 308.1 innings on one or fewer days rest, or 58.8 percent of his total innings. He's the most used reliever in baseball - over a period of seven years - often working on little rest; it wouldn't be surprising if he began to break down.

This isn't to say that Clippard can't turn things around - Chris Young and Koji Uehara are examples of older two pitch pitchers who have found ways to be successful in their mid-late thirties while running high pop-up rates, low ground ball rates, and far slower fastballs than even second-half Clippard produced.

With regard to our original question, there are a couple reasons why Clippard might still be a free agent.

In the hypothetical scenario where he is injured, he becomes a less urgent signing for teams, potentially requiring only a minor league deal. But, if he feels that he is completely healthy, having completed his fifth-straight season of at least 70 innings pitched and posting a sub-3.00 ERA, it's easy to understand why his representatives might insist upon a multi-year deal.

However, given how essential his high release point, fastball command, and fastball velocity are to his success, it's equally understandable why teams would balk at that idea. In the end, chances are he'll accept a one-year, incentive laden Major League deal with a team who can afford to take a chance on his upside.

. . .

Spencer Bingol is a Featured Writer at Beyond the Box Score. You can follow him on Twitter at @SpencerBingol.