I'm sure I've seen an article on this somewhere, maybe in one of the
diabetes magazines. You could check their web sites. Also look for the book
Diabetic Athlete for some tips & tricks. Try googling diabetes football
player for other articles; here's one --
http://www.sportsmedicine.upmc.com/MySportFootballDiabetes.htm

Does this player also use insulin?
What is the particular concern?
If it's a question of "can he?" then yes -- at least, diabetes per se
doesn't rule it out -- but it takes care & attention & it may not work out
for a particular person. However, there are quite a few professional
athletes with diabetes, as well as many high-school & college players in
various sports.
bj