Osuna making history at back of Toronto's bullpen

If you didn't know who Roberto Osuna was entering the season, you'd probably be forgiven.

Actually, if you didn't even know who Osuna was in July, it'd still be more than understandable. Why would you? Osuna missed most of 2014 while recovering from Tommy John surgery, and then put up a 6.55 ERA in the 22 innings he was able to pitch … for Class A Advanced Dunedin. The year before, it was a 5.53 ERA for short-season Class A Lansing in 10 games before his elbow gave out. Though Osuna's talent was undeniable, that's not the kind of resume that writes a ticket to the big leagues.

Fast-forward to Wednesday, where Osuna required only five pitches to finish off Wednesday's 7-1 Toronto win, meaning he's now retired 22 of the 23 hitters he's faced in the postseason. Osuna isn't just closing out games for a team that's two wins from the World Series; he's doing things that have essentially never been done before. No rookie has ever allowed a lower postseason batting average (minimum of six innings).

As impressive as that .014 average is, that's not the number that stands out about Osuna, nor is it the 96.1 mph he averages on his fastball, per Statcast™. It's "20," his age, which is to say he's the youngest pitcher in baseball this year, half the age -- or less -- of teammates R.A. Dickey and LaTroy Hawkins. Dating back to 2000, only 14 other pitchers have had a season of 50 innings pitched at 20 or younger, and the list is just littered with superstars -- think Felix Hernandez, CC Sabathia, Clayton Kershaw, Madison Bumgarner, Zack Greinke and Jose Fernandez. It's difficult to pitch a full season at 20 and not be very special (though not impossible, as Marcos Carvajal would tell you, if you could find him).

Video: ALCS Gm5: Gibbons praises Osuna's season, potential

Now, if we were just going to point out that Osuna came up at a young age and had a very good season, that'd be one thing. But there is, of course, more, because he wasn't even the only 20-year-old to jump from Class A to the big leagues on his own team. (Miguel Castro, six weeks older, did so as well, briefly claiming the closer's job before getting sent down, dealing with injuries and eventually landing with the Rockies as part of the Troy Tulowitzki deal.)

Osuna was named the closer in late June after Brett Cecil and Castro were unable to hold on to the job, and he ended up finishing 39 games. He appeared in 68 games, a record for pitchers 20 or younger. Despite his late ascension to the position, he's one of just three pitchers to finish at least 30 games at 20 years of age or younger, and the only one to do so for a playoff team:

Most games finished, 20 years or younger, 1871-2015
1. 45 -- Terry Forster, 1972 White Sox
2. 43 -- Billy McCool, 1965 Reds
3. 39 -- Osuna, 2015 Blue Jays

To put a completely unfair comparison on him, Osuna's numbers look eerily similar to Jacob deGrom's, at least in terms of strikeout percentage (27.7 for Osuna, 27.3 for deGrom), walk percentage (5.9/5.1), HR/9 (0.90/0.75), and ERA (2.58/2.54), with the obvious exception being that deGrom put those up with a starter's workload. When deGrom was 20, he was hitting .243/.294/.271 as a freshman shortstop at Stetson University.

How is Osuna doing it? The heat is the obvious draw, and indeed that four-seamer ranks 28th of the 298 pitchers to throw 300, slightly behind Matt Harvey and barely ahead of Wade Davis. But it's really the slider that comes in at 88.5 mph, 19th hardest among the 295 pitchers to throw at least 100, that's his out pitch, since hitters fail to make contact 52.6 percent of the time they swing at it. (He allowed just six hits on it all year long, which is why recent reports of a finger injury that may hinder his slider were so concerning.)

Osuna won't be in the American League Rookie of the Year Award conversation, not with Francisco Lindor, Carlos Correa and Miguel Sano easily atop the balloting, but that's not really the way he or the Blue Jays are looking for the season to end. For all the attention paid to the back end of Kansas City's bullpen, Toronto also has a pretty impressive shutdown closer. Osuna just happens to not have been born the last time either team won the World Series. So far, that hasn't been a problem.