Just copying my post from the Community Event Thread:
COTW is a Batter vs. Pitcher duel, you being the batter while facing the pitcher (AI) each week. Of course who you'll hit with, which pitcher you'll face, what stadium you'll be in, etc... will change week to week.
Basic Rundown: You get one free session each week (3 outs) and after that, .25 cents per play (think video arcade!). They will also offer packs (5 sessions for $1 and 26 for $5).
Each ball hit in play, how far it was hit (foul balls also count but won't be as much) will accumulate points as you go. You'll also have "X's Bonus" points which you'll want to strive for as that will drive your score up immensely, however, these "bonus" challenges will vary each week. (i.e. hit streaks, total hits per out, etc...) just to give you an idea. Also, every 3 hits in play will increase your difficulty (Veteran, All-Star, HOF and Legend - you start on Rookie). As you advance levels, you'll be rewarded with a nice momentum boost!
This mode
WILL test your patience at the plate! You'll want to stay alive as long as you can per strike (each strike looking will reset your "active" points). Whatever points you've accumulated in that strike session will be added to your total count.
What also makes this mode appealing is the prizes you can win each week (signed jerseys/baseballs, etc...) and don't forget, they'll have monthly prizes (Sony products, etc...) and a grand prize at the end which is why you'll want to remain active in this because your total User score will carry on as you go throughout the season.