Toph uses her sense of the pitcher's position and movements to judge the speed and trajectory of the ball. Getting to base? That's easy, she always knows the layout of the field and can feel the positions of all the players through the Earth. TOPH IS JUST THAT AWESOME.
Can she really judge when the ball's coming? I was under impression that as long as it's in the air, she really cannot know. Pfft, I can accept this theory. Toph is MOTHERFUCKING BADASS.
If her knowledge of math and physics is good enough, yes. She should be able to calculate speed and trajectory. Wind is a factor that may mess it up a bit, so her mileage may vary.
Now the question is how good her knowledge of math and physics is. I don't think there was anything in the series to support that, but nothing that went against it either, so it's anyone's game.
She's probably learned a good amount of physics without realizing it through sensing how her opponents move. I can imagine she'd stink at the game at first, but then figure out how to gauge the ball's movements and practice until she's mastered it.