Baseball finds itself in a difficult position. On the one hand, there’s a clear, increasing emphasis on bullpen usage, as starters are throwing fewer and fewer innings every year. Teams are leaning on their relievers now more than ever, and as a consequence, more relievers are getting more money. The money tends to go where it’s needed. Yet on the other hand, relievers have this nasty volatility habit. They’re tougher to predict from one year to the next one, and many of last offseason’s free-agent contracts for relievers didn’t work out very well. Teams want relievers, and teams will pay for relievers, but it’s not always easy to know which effective relievers are for real. So many end up shooting stars against the night sky.

There are your pop-up relievers, though, and there is David Robertson. It’s true that a player is only consistent until he isn’t. Every career comes with some unknown and unknowable expiration date. Perhaps Robertson is about to enter his shakier years. But over the past several seasons, few relievers have been so steady, so dependable. Few relievers would appear to come with so high a floor. In large part because of that reason, the Phillies have signed Robertson for two years and $23 million. It’s not the three years Robertson was said to be looking for, but as he’s headed into his age-34 season, I think that both sides can call this a win.

There is a little bit more to the deal. Robertson will be paid $21 million over the next two years. Then there’s a third-year club option worth $12 million, with a $2-million buyout. In other words, this could end up worth $33 million over three years, but the way club options work, the Phillies will only pick that up if they think Robertson could get even more in free agency. The potential third year is a plus for the ballclub, while both Jeurys Familia and Joe Kelly got their third years guaranteed.

None of us are in position to know very much. We do know that Robertson fired his agent and represented himself, so perhaps one might suggest that he didn’t hold out for a guaranteed third year hard enough. But Familia is going into his age-29 season. Kelly, 31. Among last year’s free-agent relievers, Wade Davis was going into his age-32 season. Jake McGee, 31. Bryan Shaw, 30. Tony Watson was going into his age-33 season, but he also got a relatively low salary. Robertson is just older than the others, which increases his longer-term risk. It’s also worth noting that an agent usually gets something like a 5% commission, so by representing himself in the market, Robertson probably saved seven figures. It’s not a bad idea for someone willing to spend an awful lot of time on the phone.

So, the consistency. Let’s get to that. By what definition has David Robertson been consistent? In each of the past nine seasons, he’s thrown between 60 and 70 innings. He’s never been hurting for strikeouts:

Primarily because of the whiffs, Robertson has maintained a fairly steady better-than-average FIP:

Robertson has been a good reliever for nine straights years. His average fastball last season was 92.6 miles per hour. His average fastball as a rookie was 91.4 miles per hour. His body has held up, and his stuff has mostly held up, although it is interesting that, underneath all the consistency, there have been marked changes in Robertson’s strategy:

You can clearly see how Robertson has backed away from his fastball, in favor of his curve. Last year, he threw more curves than fastballs for the first time in his career. There were also continuing signs of a slider, a third pitch in between Robertson’s primary two. There are both good and bad interpretations of the data, and I think both are valid. On the negative side, Robertson’s fastball has become decreasingly effective. On the positive side, he’s been able to adjust to that over time, and his numbers haven’t suffered at all. The mark of a good, long-term big-leaguer is the ability to stay good while making necessary adjustments. The fastball might never recover, but as a guy who leans more on his breaking balls, Robertson still works. He can still get hitters out, and he can still make hitters miss.

As far as the headline here is concerned, there’s something else about Robertson that makes him particularly interesting. The Phillies have reportedly been looking for left-handed help. They were in on Andrew Miller, and they’ve been linked to Zach Britton, to say nothing of a handful of left-handed starters. The front office has already acquired Jose Alvarez and James Pazos. Adam Morgan is a lefty. David Robertson is a righty, and a righty is the very opposite of a lefty, but you could say Robertson pitches like a lefty. Let me tell you what I mean.

We have splits going back to 2002 on FanGraphs. I looked at every pitcher who, since 2002, has faced at least 1,000 lefties. Robertson has allowed the fourth-lowest wOBA to lefties (.243), out of 387 guys. Looking at the same but just among right-handed pitchers, Robertson ranks third out of 328. Robertson actually has a strong reverse split. Here’s a table of the biggest reverse splits among righties who’ve faced at least 1,000 righties and 1,000 lefties:

That’s Robertson in second, out of 323 names. On average in the sample, lefties hit the righties better, by the tune of 19 wOBA points. But lefties hit Robertson worse, by the tune of 50 wOBA points. Over just the past five years, the split is 53 wOBA points, so this isn’t some early-career artifact. David Robertson is not a left-handed reliever, but does it really matter as long as he gets the lefties out? The Phillies aren’t short on right-handed weapons. Robertson is someone they can feel comfortable using in any situation.

And that is, presumably, the plan. The Phillies won’t yet commit to Robertson as the regular closer, because I don’t think the Phillies intend to use Robertson as the regular closer. They’ll also use Seranthony Dominguez, and other relievers, and it’ll all depend on how the specific games are lining up. Robertson has been a closer, and he’s been a non-closer, and he’s not going into this blind. He knows he might show up in almost any inning, particularly the later ones where tough lefties might be coming up. Whether that’s the sixth or the ninth, so be it. Robertson understands what he’s getting into.

This isn’t the move so many people have been waiting for the Phillies to make, but then, there’s been more than one move to be made. In signing David Robertson, the Phillies beat out the Yankees, and they’re taking another small step toward playoff contention. Yes, it remains true that relievers are volatile. Yet Robertson has been about as steady as it gets. All the Phillies want is another two years of the same, and it shouldn’t be too much to ask.