Bernd Leno or Kepa Arrizabalaga in goal? Laurent Koscielny or David Luiz at centre-back? And where do you start picking a strikeforce?
Arsenal and Chelsea meet on Saturday in the latest meeting of two of the Premier League's top six.
Such is the strength of their squads, managers Unai Emery and Maurizio Sarri have difficulty selecting a starting line-up each week, but we're asking you to pick a combined XI using players from both clubs.
It won't be easy. But just to get you started here's what you came up with last time.
Has much changed in five months?
There were eight players from Chelsea in the most popular combined Arsenal-Chelsea XI selected by users before the teams met back in August.
That weighting appears to have been backed-up by the performances of both clubs since, with Maurizio Sarri's fourth-placed side starting this contest a position and six Premier League points better off than Arsenal.
Mesut Ozil, Laurent Koscielny and Pierre-Emerick Aubameyang were the only players to feature for the Gunners in that XI.
The Arsenal fan's view
Akhil Vyas, The Gooner Ramble
The Chelsea fan's view
Ramon Isaac, Moving Meadows blog
Pick your combined XI
So who will be the most popular selections this time around?
You can select your strongest side from both squads, and share it on social media using #bbcfootball
My Arsenal-Chelsea XI
Pick your XI from our list and share with your friends.
Select formationConfirm team
Source: bbc.com