I admit it -- I was never a Belieber. At least not when it came to Shane.
Shane Bieber was on my radar plenty as a prospect; you couldn't miss those walk rates as he never walked more than 2.5% of opposing batters at any level until he got to Triple-A, where his control went completely off the cliff and he walked all of ... uh, 3.4% of batters he faced. He was always working with fairly average stuff, though, and never missed all that many bats, which was partly evidenced by strikeout rates that were good-not-great, usually below one per inning. He was homer-prone, however, which is unsurprising for a guy who throws a ton of strikes and doesn't have a plus pitch.
This year, however, Bieber has been a different pitcher thanks to tweaks to several of his pitches. He's still homer-prone, but he's missing so many more bats that he's minimized the damage. He throws harder now than he did in college, and the velocity was there in his unremarkable debut last year. He tweaked the grip on his changeup, getting five more inches of horizontal break on the pitch this year, but his slider was his most effective pitch in 2019 -- 43% of his swings and misses this year came on his slider. Most important, I think, is that he cut the use of his four-seamer, so that he's now throwing his three secondaries a majority of the time. He gave up 18 of his 30 homers this year on the four-seamer, meaning he gave up 60% of his homers on a pitch he threw 44% of the time, so using it less is a smart move.
Bieber is fifth in the American League in fWAR as I write this and seventh in Baseball-Reference.com's WAR, so he has undeniably been an ace this season. If his slider, which is actually breaking a little less this year than in 2018, really is this kind of swing-and-miss pitch, I see he no reason he can't be one for several years to come.
So he leads my annual column of players I was wrong about -- always on the low side, as it's no fun for anyone to talk about players I thought would be good but ended up flaming out, especially not for those players. You can see previous versions of this column for 2018 | 2017 | 2016 | 2015 | 2014 | 2013 | 2012.