What do the following football clubs have in common?
Blackpool
Bolton Wanderers
Brighton & Hove Albion
Cambridge United
Cardiff City
Chesterfield
Crystal Palace
Doncaster Rovers
Forest Green Rovers
Fulham
Hereford United
Lincoln City
Newport County
Northampton Town
Notts County
Plymouth Argyle
Portsmouth
Scunthorpe United
Southend United
Stockport County
Sunderland
Swansea City
Swindon Town
Tranmere Rovers
Walsall
Wrexham
Yeovil Town
York City
are they all grounds you’ve refused to travel to following poor performances the previous week? 
They’re football clubs, not football grounds Eric. Didn’t your RGS teacher tell you to always read the question?
Have they all had an artificial pitch?
I’ll take a punt on: We have had a player sent off against them.
Edited to add: Nope. Crystal Palace at least rules that out
They all have a Head Coach and not a manager
Have they all had a period of time where they didn’t play at their own ground and had to groundshare?
Wild guess
Are they clubs that have never won an EFL or Premier League divisional championship? In other words? Any promotion that they have earned has been either by not finishing top of the league or via the playoffs?
Lots of them have had pretty terrible owners…
Has Neil Warnock managed them all?
Sunderland have been champions of England about 5 times
They all have an association with birds either in the nickname or club crest
They’re all bastids?
They all listed in this question?
Mat Bloomfield scored against them?
Do they all have planning permission for their training grounds?
Loving the guesses, if no-one gets it by 3pm tomorrow, I’ll post another clue and then the answer on Friday.
They could all beat us at the moment?
If that was right then the list would be a lot longer.
Hmm good point..