Police have called for the suspension of FIFA's substitution rule for the South Coast derby clash between Portsmouth and Southampton in the Carabao Cup third round.
The current rule, introduced at the start of this season, requires players to leave the pitch at the nearest point when replaced instead of walking to the dugout.
While this was done to reduce time-wasting, there are fears it could endanger players during what is expected to be a febrile atmosphere at Fratton Park.
Portsmouth Supporters' Trrust secretary Donald Vass explained: 'During the game, police will advise that the new rule instructing players to leave the pitch by their nearest touch line should be relaxed.
'A decision on whether or not to hold away fans back after the game, allowing home fans to dissipate, will be taken nearer to the fixture.'
There will also be no designated 'away' pubs for visiting fans, who have been advised not to drink before the game.
Vass said: 'For away fans opting to travel by train, there will not be any 'football special' trains laid on as there will also be many commuters travelling around the same time.
'Away fans will be advised not to drink in Portsmouth, and there will be no 'away designated' pubs.'