Paul Cook told Gareth Evans to accept his punishment and do his time after his red card appeal failed.
The Pompey midfielder was sent off in the dying moments of last week’s 3-1 win at Cambridge United for a late challenge.
The Blues submitted video evidence in a bid to avoid a three-match suspension.
But the appeal was rejected and Evans now starts his ban, starting with tomorrow’s trip to Newport County.
Cook confirmed there would be no further internal punishment but has warned future offenders that his stance may change – depending on the crime.
The Blues boss said: ‘For me, the discipline comes from losing your place in the team. That is a big enough punishment for him.
‘If you know Gareth, he is a great kid.
‘He works so hard and there is not a malicious bone in his body. It was clumsy (the challenge).
‘The game was done so why he went for it is beyond me, but everyone makes mistakes.
‘If I felt someone got sent off and let everyone down, I would come down heavily on them. But not for that.’
Meanwhile, Cook believes his assistant, Leam Richardson, is facing a possible one-match touchline ban after he was sent to the stands and charged with improper conduct for his half-time altercation at the Abbey Stadium last Saturday.
‘Leam has accepted his charge and apologised,’ said Cook.
‘I think it might be a one-game touchline ban.
‘We would be the first to admit that he shouldn’t be encroaching on to the pitch.
‘We all want referees to have an easier ride. But it (Cambridge’s opening goal) wasn’t a good decision so it’s tough to sit back and take it.’