Good grief some things die hard.... (football, not just Rams)

Was just sending a text to my grandsons asking about this upcoming weekend.... decided I'd us the teams' nicknames and almost, (I edited it at the last second), sent this:

"Of the 4 games next week which is the hardest to choose? Rams vs Packers? Colts vs Bills? Browns vs Chiefs? Bucs vs Saints?"

All of you can spot the error, but can you figure out "why"?