In some ways, it's a surprise that Darren O'Day even had a career. He didn't make his college team as a freshman, and he eventually entered pro ball as an undrafted free agent in 2006, for the modest bonus of $20,000. Since then, O'Day has passed through four organizations as a Rule 5 Draft pick (once) and on waivers (twice). He's never been a team's closer, his fastball tops out at 88 mph and he turned 33 in October.
Needless to say, that's not the type of profile that generally earns a four-year, $31 million contract, as O'Day did to stay with the Orioles. In addition, because O'Day has only 14 saves in those eight seasons, a lot of fans are going to be absolutely shocked at the investment. But it's a continuation of the lesson that teams aren't paying for saves, as we saw when the Yankees gave $36 million to the dominating Andrew Miller and his one career save last year. They're paying for performance -- and while O'Day may not have the velocity or the traditional late-inning numbers, he certainly has the production.
O'Day can point to two very convincing trends over his four seasons with Baltimore -- the fact that he kept allowing fewer earned runs, and the fact that he kept increasing his strikeout percentage, two numbers that are not unrelated.
Over the past three seasons, of the 307 pitchers to throw at least 150 innings, only Dellin Betances and Craig Kimbrel had a lower ERA than O'Day's 1.79. While ERA for relievers is imperfect for a lot of reasons, it's pretty hard to put up a number like that by accident. O'Day's strikeout rate is higher than more celebrated closers Glen Perkins or Sergio Romo. He doesn't get the glory, but he keeps runs off the board.
So how exactly does a soft-tossing righty do that? The obvious answer would be the unusual sidearm delivery, but that quirky aspect of his game alone isn't enough to explain this. Instead, it's got everything to do with approach and movement, and what O'Day's pitches do that others can't replicate.
In 2015, there were 389 pitchers who threw at least 200 four-seam fastballs. 381 of them threw harder than O'Day. But only one of them, San Francisco's Hunter Strickland, had a higher swing rate on it than O'Day's 59.8 percent. Only one of them, the otherworldly Aroldis Chapman, had a higher swing-and-miss rate -- or whiff percentage -- than O'Day's 36.8 percent.
As you can see from the following graph, O'Day finds his fastball in a very favorable position in the upper right quadrant, which is to say, batters swing at it a lot, and they miss it often:
But Strickland averages 97.4 mph on his fastball; Chapman, 99.9. Clearly, O'Day is doing something to overcome his velocity issues. In this case, it's not about spin, as his four-seam spin rate of 2,317 rpm is essentially league average. It's about his approach and his grip. Unlike most sidearmers, O'Day isn't trying to get grounders, as he admitted to local media in 2013. He's trying to throw it high, because he believes -- rightfully -- that's how he'll get swings, and the way he releases the ball with his middle finger underneath allows him to get the kind of "rise" you just don't see from a sidearmer, which helps him get misses.
When O'Day does it right, it does things like this, which batters can't resist swinging at (it is, after all, only an 88 mph fastball):
But even when they do make contact, they rarely make solid contact. O'Day's average Statcast™ exit velocity of 82.2 mph is the second lowest among the 407 pitchers with 100 fastballs thrown. He's not kidding about throwing it high, either, because 24.9 percent of his four-seamers are three feet or higher off the ground, 15th most in baseball. Though he also has a sinking fastball, O'Day's game is simply "fastball up, slider low," as these heat maps show:
Now, about O'Day's slider: It's the lowest-spin slider in baseball, coming in at just 936 rpm, when the average slider is 2,090 rpm. It came in at 2.5 feet or lower 39.7 percent of the time, the fifth-highest rate in baseball (unsurprisingly, Romo was first). Like the fastball, it's just not hit hard, averaging only an 81.9 mph exit velocity, which is excellent. It's incredibly difficult for hitters to react to the possibility of both high fastballs and low-spin sliders thrown low, particularly from an unusual angle.
O'Day has now been outstanding for four consecutive years, with evidence he's improved. He threw that low-velocity fastball 349 times in 2015, and allowed a .097 batting average against it. O'Day is in a free-agent marketplace where there's not really an elite reliever (barring a pricey Chapman trade) for him to compete against, with Joakim Soria and Tony Sipp likely the best options. No, he doesn't have saves, but also saves don't matter (not to mention, Zach Britton exists).
Under the radar though O'Day may have been, he's done nothing but get outs for years. Baseball doesn't pay for saves any longer. Teams pay for outs, no matter what inning they come in. O'Day may not look the part, but he's earned his riches.
Mike Petriello is an analyst for MLB.com and the host of the Statcast podcast. He has previously written for ESPN Insider and FanGraphs. This story was not subject to the approval of Major League Baseball or its clubs.