You have 10 minutes - 50 players will flash up. All you have to do is tell us whether they played for Chelsea, Liverpool, both or neither.
Remember to tweet your scores @FourFourTwo, and challenge some friends while you're at it.
Whenever these two play, it's usually a stunning match – just look at the League Cup final.
There's plenty that separates these two sides. One's from the northwest, the other from London; one plays in blue, the other in red. But there's plenty that they have in common, too.
We're not just talking about their German press-happy managers. We've made a list of a half-century of footballers who might have played for Chelsea, for Liverpool, both or neither. Can you remember?
Take your time with this one, as there are quite a few names on there that you probably haven't seen for years...
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