I tried that at first (IA, IL, IN, MN, etc), but then I quickly realized that it wasn't very easy to quickly identify what teams were playing. For someone who lives and breathes Big 10, it probably would work ok.
I'm leaning toward keeping it the way it is right now. I might use Illinois' full name: due to the font not being fixed-width, it really isn't any wider than "Purdue" despite being two letters longer. I might do the same with Indiana as well.
EDIT: I did change it to use "Illinois" and "Indiana". I tried "Ohio St" and "Penn St", but I didn't like it -- the extra spaces hurt readability.