Last year, Mitch Garver didn't enter the season as the starting catcher for the Twins. He wasn't even clearly the primary backup initially -- in the season's first eight games, he and Willians Asudillo each started twice, behind Jason Castro's four. Five months later, he hit the home run that broke the all-time single-season record for a team. By the end of the season, he'd popped 31 dingers, won a Silver Slugger Award, and by some measures, he was one of baseball's 10 best hitters.

Entering 2020, Castro is gone, and Garver is the clear starter ahead of Alex Avila. After posting a massive line of .273/.365/.630 (156 OPS+) that was legitimately one of the most unexpected breakouts in years -- no, seriously, we can back that up -- there's only one question Twins fans are interested in: Can he do it again?

It's a fair question, because Garver hadn't exactly done a lot to predict this kind of performance. In 387 plate appearances over 2017-18, he'd put up a 99 OPS+, or "league average," and while a league-average bat is welcome from a backup backstop, it hardly gave a lot of indication that he could do what he did in 2019. Plus, he was 28 years old all of last year, so it's not like he was a terribly young player getting his first taste of the bigs. Plus, how can you possibly talk about a 2019 power breakout without mentioning the changes in the ball that made it more aerodynamic?

If all of that gives you pause about what to expect in 2020, that's absolutely right. It should. He didn't do it in a full season, and he doesn't exactly have the track record to demand the confidence otherwise. Projection systems, understandably, aren't fully buying in yet. Because they take into account multiple years, the various methods have him as "slightly above-average" for 2020. That's a 109 wRC+ from ZiPS, a 108 wRC+ from Steamer, and a 104 DRC+ from PECOTA, where each set 100 as "league average."

But remember, he wasn't just pretty good. He was really good. There were 241 hitters to step to the plate at least 350 times, and Garver was the seventh-best among them. He outhit Anthony Rendon, Pete Alonso and Aaron Judge. He outhit just about everyone, and he did it as a catcher -- it was the second-best hitting season (of at least 350 plate appearances) in Twins/Senators history from a catcher, behind only Joe Mauer's 2009 MVP season.

So: How exactly did he do that? And is there anything in there that might give us a little extra confidence about him. There sure is.

1) Garver's 2019 breakout was nearly unprecedented recently

OK, so about that "most unexpected breakout" bit -- let's back that up.

We dug into an entire decade's worth of Steamer preseason projections, dating back to 2010. Projections aren't predictions, nor do they try to be, but they do a good job of setting data-based expectations for the coming year, even knowing that there's always going to be an injury here or a breakout here that absolutely no one could have seen coming.

With that data in hand, we looked for all players since 2010 who were projected to have at least 200 plate appearances in the coming season and then managed to get at least 350 plate appearances in reality. That gave us 2,161 different player seasons, and across that aggregated sample, Steamer actually did extremely well -- it projected a .766 OPS, and the actual outcome was .761. This isn't a perfect method, because it won't collect the true out-of-nowhere guys like Yordan Alvarez, who weren't projected to get much playing time at all, but this does help us get to guys we thought we knew something about.

Garver, entering 2019, was projected to have a .723 OPS. Garver, in reality, had a .995 OPS. That's a difference of 272 points of OPS, and out of 2,161 players ... that's the third-largest overperformance. We found 17 players who overperformed by at least 200 points. You'll probably recognize the other names on this list.

Those are some names, right? Right away, this is a good start; every single player on this list had or is having a Major League career of some note.

Excluding the 2019 ones, which we don't know enough about yet, these fall into a few categories, like:

The young legends having a first great year: Mike Trout, Bryce Harper, maybe Aaron Judge

The controversial year you're giving a double-take to: Marwin González

The mid-career swing-changers: J.D. Martinez, José Bautista, Daniel Murphy

The never-repeated career year: Zack Cozart, Mike Napoli, Randal Grichuk, Josh Hamilton

So, which one is Garver? He's clearly not in the Trout/Harper tier, but is he more of an older breakout guy? Or was this a fluke?

2) Garver stood out in some impressive metrics in 2019

It's one thing to say "he hit well," because he obviously did, but we're trying to figure out how he did it, and how much might be attributed to the ball.

A good place to start is simply with "how hard did he hit it," which is important; based on everything we know about the effect of the ball itself, the major impact is on distance flown in the air, not how hard it's hit at the point of contact. The answer: Really hard.

Garver ranked ...

• Sixth in hard-hit rate (50%)
• Seventh in average exit velocity on flies+liners (97.2 MPH)

The names ahead of him were primarily Judge, Miguel Sanó and Nelson Cruz, so you can see why that's impressive. Now, let's include the angle at which he hits the ball, because hitting it hard into the ground isn't quite as useful.

• 14th in barrels per batted ball (15.5%)

(A barrel is the perfect combination of exit velocity and launch angle, even if it's a blast robbed by a great defensive play or a stiff wind, and again, we haven't touched on anything about distance yet.)

Put another way, including quality of contact and amount of contact, Garver hit like DJ LeMahieu or Pete Alonso -- albeit in not nearly as many plate appearances.

Now, a lot of that damage came against fastballs. A lot. We have reliable pitch-tracking data going back more than a decade, to 2008, and if we look at every player season where a hitter had at least 100 plate appearances end in a fastball -- this is thousands of seasons -- check out the top five in Weighted On-Base Average against them:

Best performances against fastballs, 2008-19

• .523 -- Albert Pujols, 2008
• .515 -- J.D. Martinez, 2017
• .512 -- Franklin Gutierrez, 2015
• .505 -- Josh Hamilton, 2010
• .502 -- Mitch Garver, 2019

Gutierrez is a weird one, but the other three are some all-time great seasons. Next on the list: Jim Thome's 2010, Harper's historic 2015, David Ortiz's 2012, Miguel Cabrera's Triple Crown 2013 and Juan Soto's 2018. It's quite the group.

"I'm a great fastball hitter," Garver said to MLB.com's Do-Hyoung Park last month. "Everybody now knows that."

Of course, he hit only .182 with a .348 slugging against non-fastballs, so that's the real test here for 2020 -- he's likely to see a lot of breaking stuff until he proves he can handle it.

"He went on to say that he's been focused on hitting a different kind of offspeed pitch every day," wrote Park, "with the goal of better recognizing such pitches out of the hand and also figuring out how to put his body in the best position to do damage on such pitches without sacrificing his ability to get on the fastball."

That's all well and good for 2020. But: What happened to cause last year's breakout?

3) What made Garver break out in 2019?

Garver didn't entirely come out of nowhere, of course. He won the Twins Minor League Player of the Year award in 2017, and his 2014 performance in Class A was one of the best full-season hitting lines of the Minor League season that year. Still, he'd followed that up by hitting only .245/.356/.333 in 2015, and he'd never made a Top 100 list at any of the major prospect outlets. In 2017, for example, MLB Pipeline had him behind 23 other Twins prospects, though they accurately stated that "he makes consistent hard contact with a short and compact swing."

And then ... this. How?

“I didn’t wake up this good,” he told the Star-Tribune last fall. “It’s not a mistake. It’s not magic. I made myself.”

Part of that, it seems, echoes the swing changes of Martinez, Murphy and others.

"I showed him some things to work on last winter," Garver's personal hitting coach Jason Columbus told the Albuquerque Journal last summer, "and he put in a ton of time revamping his swing." ("He was trying to hit .300 and drive the ball the other way," Columbus said about Garver's approach before joining him, which explains a lot about both how important intent can be and how the previous Twins regime functioned.)

It's become somewhat played out to talk about the "launch angle revolution," which obviously doesn't describe everyone or work for everyone, but it's difficult to ignore what the metrics say -- in 2017-18, his fly ball rate was 23%, but in 2019, it was 35%. If you can hit the ball as hard in the air as he can, why wouldn't you want to put it in the air?

"I'm actively trying to hit home runs, fly balls," Garver told The Athletic.

"I think home runs are the coolest thing you can do," he later continued. "That’s how much I love them. That’s why I try to hit them every at-bat."

It's not as simple as "try to improve and you'll improve," but then again, we've seen Garver put a ton of work into his pitch framing behind the plate and have those numbers get better as well.

The caveat, obviously, is that Garver just hasn't done this for that long. Even now, he has only 746 plate appearances in his Major League career, and in his breakout 2019, he went to the plate only 359 times. We know he's far weaker on breaking balls than fastballs, and now so does every pitcher in the bigs. If you wanted to take the under on Garver exactly repeating his 2019 line, you'd be well-advised to do so.

But that's not the same thing as turning back into a pumpkin, either. When you look back at some of the more unexpected breakouts of the past few years -- Cozart's 2017, which was completely unsupported by underlying metrics, comes to mind -- there were reasons to question how "real" a few of them were. You might be able to fake your way into a good half-season; it's really difficult, if not impossible, to fake your way into hard-hit numbers like the ones we've shown. Garver probably won't be the best hitter on the 2020 Twins, not with Cruz and Josh Donaldson around. But we'll take the over on his relatively middling 2020 projections, based on what we've seen. It feels like he's earned that much.