Etiquette Question

In one league, I've already locked first seed for the playoffs. My opponent this week has a win-and-in. Am I expected to throw the match?

Does it make a difference that this particular opponent gave me my one loss of the season, and I want to beat them? And that it's more fun if I actually try? But I don't want to come off as a massive dick, since I don't actually need the win.