I wouldn't even label it as "concerning"... it's terrifying!
18.1
16.0
15.4
17.4
23.9
28.4
Where the hell did those last two years come from?
increased aggression as he desperately tries to turn around his offence because he realizes that his chances to stick in the bigs as anything more than that suboptimal guy who only starts on a garbage team are quickly running out?
looking at his pitch f/x and plate discipline profiles, it also looks like opposing pitchers are increasingly catching on that he's overmatched against breaking balls. Beyond just the K-rate, his last 2 years are marked by a pronounced shift toward more sliders/curves and less fastballs, along with a much more aggressive attack plan with 1st pitch strikes. This in turn shows up with his swing rates not really changing, but his contact rates plummeting and swinging strike rates shooting up.
From what I saw of him with the Sox and Athletics over the last couple years, this bears out on the eye test too. He remains hyper-aggressive at the plate, which leads to a lot of bad hacks at pitches he should let go, and a lot of balls he rolls over on and has to make a mad dash to 1st to beat the throw. It's like watching Pillar combined with Kawasaki.