Plenty of players have represented both Chelsea and Monday's opponents West Ham United, but do you know which of those two clubs each of them made the most Premier League appearances for?
We host the Hammers at Stamford Bridge tomorrow evening as east meets west in a London derby. Despite the local rivalry between the two sides, 13 different players have featured for both in the Premier League so far, including more than a few of Chelsea's title winners who started their careers with the Hammers.
All 13 of those players to have appeared on both sides of the capital are included below, all you need to do is identify if they played more games in the Premier League for Chelsea or West Ham. Good luck!
If you fancy using that Chelsea knowledge to try to win some fantastic prizes while competing against your fellow Blues fans, don't forget to enter the Play Predictor for Monday's match.