England squad reminded of their responsibilities - Burnley keeper Nick Pope
Tammy Abraham, Ben Chilwell and Jadon Sancho remain in Southgate's 30-man squad but their arrival at St George's Park has been delayed while the Football Association investigates reports the three players attended a social gathering at the weekend which broke coronavirus rules.
It is still uncertain when the trio, who were reportedly at a surprise birthday party for Chelsea striker Abraham, will be cleared to link up with their team-mates.
The incident is the latest in a growing list of off-field misdemeanours or behaviour which has seen a negative focus on the Three Lions.
Mason Greenwood and Phil Foden were sent home during the last international break for breaching Covid-19 guidelines in Iceland, while Harry Maguire had to be dropped from the previous squad after being handed a suspended prison sentence in Greece.
Maguire, who strenuously denies the charges of assaulting a police officer, swearing, resisting arrest and bribery following an alleged incident in Mykonos, has appealed against the verdict and subsequent 21-month suspended prison sentence and returned to the squad for Thursday's friendly with Wales and the Nations League games against Belgium and Denmark.
Asked by BBC Radio 5Live if Southgate had told the players what was considered unacceptable behaviour, Pope replied: "Yes, a little bit - it was more just reminders of what it means and how it can affect the squad really.
"How if just one person make a mistake it is not just affecting one person. It really goes round and affects the squad.
"Having that reminder of that responsibility it is a great thing because it proves you are not just acting on your own behalf, you're acting on behalf of the squad and, in reality, the country really."
With Abraham, Sancho and Chilwell retaining their places in the squad - Pope said that there should not be a "no-tolerance" policy in place and that mistakes will always be made.
"We're being reminded about the responsibilities of being England players and just going out on the football pitch and performing to the best of your ability," he added to talkSPORT.
"It's day in day out whether you're now at your club or in your country is something that is important to know represent your club in your country at all times.
"Some people are new into the squad or, remember as well, some people are young and it's not everyone's 30, 31, 32 and been around, seen it all and done it all.
"Some people, you make mistakes. In life that happens, it happens in football. It is important to squash these things and moving forward be better and represent ourselves better."