Jordan Obita will spend another two matches on the touchline after Pompey decided not to appeal his Oldham dismissal.
The on-loan youngster was given a straight red card for his part in a second-half scuffle with Connor Brown.
Referee Carl Berry then mistakenly sent off the Latics’ Cliff Byrne, following consultation with the fourth official.
Since then Byrne has had his red card rescinded, with the three-match ban handed to the real culprit Brown.
No such let-off for Obita, though, with Michael Appleton opting not to lodge an appeal after studying video evidence of the duo’s halfway line clash.
The 18-year-old missed Tuesday night’s win over Bournemouth and will also be absent from Sunday’s trip to Crawley and the September 15 visit of Walsall.
And for Appleton it further weakens his options.
He said: ‘We never appealed against Jordan’s sending off.
‘We had a look at the referee’s report and it’s a difficult one.
‘Jordan hasn’t hit him (Brown) as such, he has pushed him, probably in an aggressive manner.
‘As daft as it is, it’s a sending off these days.
‘It was never the case in my day.
‘Seems a little bit harsh getting three games for pushing somebody but that’s how it is these days.
‘To be honest, the incident wasn’t clear in the footage we had.
‘It’s just a bit of a shame he has been given a three-match ban as a result.’
The Blues also have Mustapha Dumbuya and Conor Clifford missing against Crawley.
Dumbuya is on duty with Sierra Leone for their Africa Cup of Nations match with Tunisia.
Meanwhile, Clifford is on Republic of Ireland under-21 duty.
Appleton added: ‘Muzzy will arrive back in the middle of next week and be here for the Walsall game.
‘Conor is going to be away as well.
‘He was due to go away Monday but stuck around for Bournemouth. He will miss Crawley, too.’