When the Cardinals signed Carlos Villanueva to a minor-league contract back in February, the other Ben noted that since his rookie season, Villanueva has never made more than 16 starts or logged fewer than 33 appearances. With the exception of one season he spent fully in the bullpen, he has also always made at least five starts. That puts him in some extremely rarified air.

When it comes to moving back-and-forth from bullpen to rotation, nobody swings like Carlos Villanueva.

Setting the parameters for what constitutes a swingman is a bit arbitrary, but Ben's initial framework seems solid - 16 or fewer starts and at least 33 appearances. That means we're talking about guys who made at least twice as many appearances in relief as starting. We'll also need some kind of floor to separate guys who were really just relievers who only made a couple of token starts. I'll set the minimum at five starts - the fewest Villanueva has made.

Under those conditions, Carlos Villanueva has qualified as a "swingman" in seven different seasons. No other pitcher since 1920 has met those conditions in more than five. (If you bump the minimum number of starts down to three, Villanueva is still the king, though a couple others come closer with six seasons.)

I was surprised to find Villanueva was in such an exclusive club, especially when looking back as far as 1920. I suppose in my mind, in that era before bullpen roles became so defined with closers and LOOGYs and the like, there were basically eight rubber-armed guys sitting out there ready to pitch in any circumstance. Their wool uniforms were smeared with tobacco and they all worked at gas stations in the offseason.

But while more than 1,000 players have met our definition of swingman in at least one season, less than 100 have done it in even more than two seasons. There seems to be a few reasons for that.

The role of swingman is often a brief stopover somewhere on the journey between rotation and bullpen. It can be a role early in the career of a young buck who projects to eventually join the rotation. Carlos Martinez met the criteria last season. It can also be a last stopping point on the way out of the league for a starting pitcher reaching the end of the line. Jeff Fassero is one of only two other pitchers in the last 20 years to log at least four seasons as a swingman. One was very early in his career, the other three were essentially at the end.

But even these criteria don't quite do justice to just how much of a swinger Carlos Villanueva is. Some pitchers who meet this criteria may not so much be swingmen as simply guys whose role changed during the season. Maybe they began the year in the rotation, faltered and were exiled to the pen. Maybe they were only in the pen to keep their innings down. Or maybe they only ever came into the rotation because all other options were decimated. Often, these guys need to be sent down for a week or two to be "stretched out." It's an even more uncommon feat to not just change roles, but to move back-and-forth.

In four of Villanueva's seasons, he's transitioned between starting and relieving at least twice, including each of the last two years in Chicago. He did that without needing to be sent down to the minors to be stretched-out.

Carlos Villanueva is such a historically unique pitcher, he really deserves a term beyond just swingman. Think of him as a utility pitcher. You can put him into whatever role you need. He has started 76 games in his career and closed out 79. Just like a position player who can play across the outfield, the corner infield positions and maybe not be too much of a butcher at second base, the versatility makes Villanueva uniquely valuable.

For much of his career, Carlos Villanueva has posted a WAR in the 1 - 1.5 range. In general, when a sudden need arises in the rotation and a team needs to pull whoever's rested from AAA, that will be a pitcher at or below Replacement Level. That's the real value of Villanueva. He can plug a hole on a pitching staff like few can. Plugging a hole may not sound like a big deal, but when your ship is taking on water, it's good to have a Carlos Villanueva around.