To hit some point being made in this thread:
Power matters. The best "demonstration" I have of this is my current power/contact 1B. As a bronze (low power) he hit a ton of gap doubles or flew out. As soon as he hit silver, and he got a "massive" power boost (from getting silver card and another power booster in the mini-diamonds) he spent some time hitting "over the outfielder's heads" (at least until they started playing me deep and they started turning into warning-track catches) and the HRs started really popping.
I don't think "slumps" are built into the game. One of my characters, all of them on beginner/default sliders, has a 100+ game hitting streak...
I have "anecdotal" evidence that pitcher stats are factored into the game. To wit, there are some pitchers (if I'm right, those with high HR/9 stats causing more hits to "stay in the ballpark" and/or high groundball rates), and others that if I compiled all my characters I probably have an .800 HR average against.
Which is the other reason why I don't think slumps are built into the game - I practice the old adage of "adapt to what you're facing" - with slight variances in my timing, the "groundball / no homer" guys I'll bang a 3 doubles in the gap night off of, and when I "mistime" them with a HR swing, I tend to "pop/line out". Then there's the ones where I lock onto my "homer timing" and watch a ton fly out...
