Linguistics and the NFL - that's the sort of unusual combo you come to AVI for.
Switching between the local stations and ESPN on the radio I have noticed that locals, both sports jockeys and callers tend to say "check," while the national commentators tend to say "chick." It's hard to measure because it goes by quickly, there is something of a continuum between the i and e, and I do hear exceptions on both fronts. I also think I am hearing an age difference, though I don't actually know the ages of the speakers, and I might be fitting the data back into my theory.
Still, here's my thought: John Havlicek. Not only was he a New England legend and likely to bleed over into anything similar, but we were much more used to Czech names and pronunciations than Croatian ones in this country until the 1990's. Dubcek, Hornacek. Even though younger New Englanders might not be familiar with Havlicek, the older sportscasters could have influenced them right out of the gate with that pronunciation. I keep saying "check" and have to work to say "chick," myself.
I don't know how the man himself pronounces his name, even after
browsing youTube. If he uses the "eh" sound himself, that would shoot
my theory to the ground. Wikipedia does give an "ih" for Bill and an
"eh" for John, though. Presumably on the basis of something.
I'd be interested what other people hear out there.