It’s impossible to know exactly who you’re going to be playing at the start of the season. Inevitably, most teams will undergo a series of significant changes that reshape their identity over the course of the year, whether positively or negatively, voluntarily or otherwise.
The Pittsburgh Steelers, for example, are a different team than the one that started the season now that rookie Kenny Pickett is at quarterback instead of veteran Mitch Trubisky. You can add the trade of starting wide receiver Chase Claypool as well.
Their upcoming opponent, the Indianapolis Colts, have significantly changed as well, most notably at the head coach position.