I did fantasy football on my own this year with 6th graders, but next year I'm using a book like one of these.

http://www.amazon.com/exec/obidos/se...rocess=default

You could also use the field to incorporate geometric fractions. A line from home plate through the pitcher's mound to 2nd base cuts the diamond in half, as does a line from 1st to 3rd (not through the pitcher's mound). A little trickier and less precise are fielder responsibilities. Left, right, and center fielders are each responsible for about 1/3 of the outfield including foul territory and overlapping (probably more like 2/5 each). The 1st, 2nd, 3rd base, and shortstop positions share responsibility for the infield including foul territory, but also overlap with the outfielders, pitcher, and catcher. It's messy, but might make for a good open-ended topic.
The baseball itself is covered by 2 identical pieces (kind of fat curved figure 8s) sewn together for an unusual example of 1/2.

You might try fraction of team to bat in an inning, fraction of strikes, balls, etc, per inning, fraction of line drives/ pops, etc when hit... hope this helps.

I'm looking for a resource that uses baseball themed math lessons. All I can think of so far is calculating batting averages, games played, etc... I was wondering if anyone else had ideas for using baseball as part of a Fractions Unit?