“You can’t teach an old dog new tricks” is an idiom that points out that as we age we become more stuck in our ways. While there is some scientific backing of this adage, it’s not actually true. For example, if any of you happen to have parents or happen to yourself be in Generation X or a Boomer, basically all of the interactions happening online are just that: an old dog learning a new trick.
So what do half-true idioms have to do with football? The Green Bay Packers starting quarterback is almost certainly an old dog.