This is not a secret, but the way that relievers are used has changed quite a bit throughout baseball history. One of the first truly famous relievers was the Pirates' own ElRoy Face, who had a dominant run from 1957-1962. In that span, he averaged 61 appearances a season with 47 games finished. That doesn't sound terribly different from the way the Pirates used Joel Hanrahan last year (63 appearances/57 games finished) except that Roy also averaged 95 innings a year, which is just about 1 2/3 innings per appearance. Saves weren't an official stat back then, but Face averaged 18 a season. Face wasn't brought in to protect leads late in games, he was brought in under any and all circumstances to finish games, no matter the situation.
That sort of pattern came to its natural culmination with Mike Marshall in the early 1970s. In 1973 with the Expos and 1974 with the Dodgers, Marshall threw 179 innings, then 208 1/3 innings in 198 total appearances, all in relief. Marshall finished 156 of those 198 games, finishing second in the Cy Young voting in '73 and winning the award in '74. All of those appearances clearly took a toll, though, as his inning total declined five years in a row before a brief, two-year resurgence with the Twins at the end of his career.
Since the '70s, we've been slowly evolving towards the current model of relief pitching, where closers pitch late in games with leads and rarely exceed one inning. Most other relievers have defined roles; there are eighth inning guys and LOOGYs and long relievers and swing men and on and on. I don't think that this is necessarily a bad thing; it seems logical to me that it could be much worse for an arm to throw 208 1/3 innings over 106 appearances the way that Marshall did in 1973 than it is to throw 202 1/3 innings over 31 starts the way AJ Burnett did last year because of the constant wear on the arm.
All of that being said, it's also not a secret that a lot of very, very smart baseball people think that strongly defined reliever roles are a stupid because the most important moment of the game is never at the same point. Maybe it's in the bottom of the 11th inning with a 1-0 lead and the heart of the Tigers' order up, but then again maybe it's in the top seventh inning with a tie game and a go-ahead runner on second. Some situations call for Jason Grilli and his mind-boggling strikeout rate and some situations call for Mark Melancon and his cutter that forces you to pound the ball into the ground, but neither guy ever gets brought into those situations because of their defined roles as closer and eighth inning guy respectively.
One of the larger and more ignored problems of modern reliever usage, though, is this: long relievers and swingmen almost universally suck. Every team has a reliever or two on the roster of throwing multiple innings or making an emergency start or psuedo-start, but these guys are almost always sixth and seventh starters. Last year the Pirates had a lot of relievers that had good seasons, but only three that topped 50 innings and worked more than an inning on average: Brad Lincoln, Chris Resop, and Jared Hughes. Lincoln was great for the Pirates, but Resop was not and Hughes completely collapsed down the stretch. If you go back to 2011, Daniel McCutchen threw 84 2/3 innings in 73 relief appearances. Daniel McCutchen!
With the Pirates' torrid start, a lot is rightly being made of bullpen usage. Besides regression concerns, neither Jeanmar Gomez nor Jeff Locke are really capable of throwing 120 pitches and giving the bullpen a night off. AJ Burnett and Francisco Liriano both rack up huge pitch counts early in games and find themselves in trouble by the sixth or seventh inning. Even Wandy Rodriguez has only finished the seventh inning twice this year. The Pirates' bullpen is throwing a lot of innings.
Still, the Pirates have done a decent job of managing Jason Grilli's innings after he nearly got run into the ground in the early season. Grilli is on pace for 75 1/3 innings, which is a touch high for a closer and more innings than he's thrown in recent years, but it's not really insane by any stretch. Joel Hanrahan threw 69 2/3 innings in 2010 when he wasn't the closer, then 68 2/3 innings in 2011 as the closer. It seems like 70 or so innings is a decent closer target and Grilli's only a little bit above that.
Melancon is a slightly different story. He's on pace for about 85 2/3 innings. This is almost definitely too high; he threw 74 1/3 innings in 2011 and was very effective all year, but he wasn't quite right in 2012 (that's not to say that fatigue affected him last year, just that it's worth considering). He's never been a starter in his career and didn't have huge minor league workloads. There's a balance point somewhere for him and I think it's probably right around 75 innings. It's not necessarily wrong for the Pirates to push him to his outer limits, if he's not wearing down and if the Pirates are in a pennant race in 2013. It's still worth considering, though, that there is a point of diminishing returns (see: Jared Hughes last year) and that there's also a point at which "Mark Melancon Clint Hurdle" will become a Google autocomplete the way "Scott Proctor Joe Torre" is. Misusing players like that reflects poorly on the team.
Still, Clint Hurdle has (for the most part) done a decent job managing their workloads given the number of close games the Pirates play and circumstances of the rotation. Both guys are a bit overused (Melancon more than Grilli), but not obscenely so (Charlie did some nice work on pitch totals for both guys which is also worth considering in this discussion, though at the same time I do feel like number of appearances/innings might be more important; it's possible that I'm being ignorant of some work that's compared pitch totals to appearances to try and figure out overuse, but I think it's more of a chicken/egg discussion). They've both only been used on three calendar days in a row once. This has been the longest set-up in the long-winded history of this blog, but what I'm getting at is that the Pirates have a rotation that routinely struggles to get out of the sixth and seventh innings, but they've managed to get good bullpen work without completely burying their two best relievers.
A big reason for this is Justin Wilson. Since April 21, the Pirates have won 13 of the 14 games that Wilson has appeared in. In those 14 appearances, Wilson has pitched more than one inning nine times. In those nine multi-inning appearances, he's entered the game in the fifth or sixth inning six times and in the seventh inning once. In those six mult-inning, early game appearances, Wilson's entered with scores of: 2-2 (two runners on base), 1-1 (two runners on base), ahead 4-2 (two runners on base), ahead 2-1 (tying run on base), ahead 3-1 (two runners on base), and ahead 4-1 (two runners on base).
Wilson's an interesting study here: the Pirates moved him to the bullpen in Indianapolis late in the 2011 season and it quickly became apparent that he was more suited to the 'pen than the rotation because his fastball velocity ticked up into the mid-90s and his ability to get swings and misses covered his control problems a bit better in the bullpen than in the rotation. The Pirates put him back in the rotation in 2012, anyway, and had him throw 135 innings. All of this makes him pretty uniquely suited for this kind of role: as a former starter, he's the one reliever that could probably handle 90-100 innings out of the bullpen this year. His control problems are also minimized because when you enter a game with a tying or go-ahead run on base and one or two outs, a walk is not the worst outcome if you're capable of missing bats and keeping the ball in the park (Wilson can do both).
This isn't to say that Wilson's walk rate isn't a concern, because it is, and it's not to say that Wilson's work rate shouldn't be considered because, as I've been saying ad nauseum in this post, working as a reliever is much different than working as a starter. I just think it's interesting to see how the Pirates groomed Wilson for this role, how well he's performed in it this far this year, and how that's helped mitigate the Pirate rotation's poor durability. It seems like Wilson's being groomed for a late inning role lately, which makes sense as a way to spell Mark Melancon some, and that Vin Mazzaro is picking up some of the longish relief work that was previously going to Wilson. Mazzaro's been good in that role (better than expected, for sure) thus far and I'm willing to reconsider his potential going forward as a reliever, but I can't help but think that Wilson's particular skillset would be wasted in a more traditional bullpen role with this particular Pirate rotation.