It appears that action on the field can adjust up

You could also spend real money on Stubs and use them to buy training points — paying to bypass the daily grind of the sport of baseball. You simply put the points wherever you wanted, raising only the attributes that you cared about (or had to maintain to avoid regression).
Sony San Diego has excised those microtransactions from Road to the Show, which is perhaps the most welcome change in the entire mode. The studio also doubled down on the idea of making players earn every bit of their athlete’s progress, by eliminating training points as we knew them. In MLB 18, the specific things you do in games determine which of your attributes go up and which ones go down — you have no direct control over raising your ratings.
If you drive in a runner with a single off a lefty, you should see increases in your contact versus left-handers and batting clutch ratings. But if you strike out later in the same situation, expect to lose some progress in those areas. If you make a throwing error, you can be assured that your arm accuracy and fielding ratings will suffer. And if you get a slugger to hit a weak infield pop-up, it might improve your HR/9 attribute.
It appears that action on the field can adjust up to three attributes at once — at least, the notification that pops up after each play never displays more than that. Sometimes, your performance won’t produce the attribute progression you’d expect, which I find endlessly annoying. I lost track of the number of times that I struck out a hitter but didn’t get a K/9 rating boost (and no, it’s not tied to swinging strikeouts — I occasionally got a K/9 improvement when I struck somebody out looking).Cheap MLB18 Stubs

MLB 18 seems to favor awarding progression of other attributes, which ensured that I ran up against those caps more quickly while my K/9 rating lagged. Now, this may be a result of picking the Control Freak archetype, which doesn’t emphasize strikeouts. But the inconsistent progression remained frustrating nonetheless. Worse still, it doesn’t appear that you make any progress if you simulate appearances; at least, there’s no easy way to check