Why isn't Terry Bradshaw on Fox's NFL show today?

It's rare that we don't see Terry Bradshaw talking about the NFL for Fox. Here's why that was the case on Sunday.
The Spun via MSN

NFL On FOX Announces Health Update For Terry Bradshaw Sunday

NFL on FOX announced on Sunday that Terry Bradshaw will be missing today's show with an illness. Bradshaw, 77, was not seen ...