The length and color of the lines changes depending on how well your pitcher can throw that pitch. When you're ready to throw, you hit the pitch button. A speed gauge begins to rise, and you simply hit the pitch button again to throw at that velocity. You can also aim using the d-pad. One thing I like is that most pitchers in the game cannot paint the corners at will, which is more realistic.
Pitches also have good velocity and realistic break, too.
Batting is also fairly strong. Hitting in WSB2K1 is both very simple and very hard. Batting is cursor based, but instead of using a location point like so many other games, you actually aim at the ball. This was very difficult to get used to at first, but after a while it became a little easier and felt more like real hitting. To hit the ball, players have to hold the R trigger button to get ready to hit, then release it to swing.