Daniel Farke felt the ref got it wrong in the game’s key moment as Pompey pulled off an FA Cup upset.
The Norwich boss believes ref Darren Bond was incorrect to send off skipper Grant Hanley in the Blues’ 1-0 third-round win at Carrow Road.
Hanley was given his marching orders after 15 minutes for bringing down Ronan Curtis in what was ruled a professional foul.
Farke insisted Curtis wasn’t presented with a clear goalscoring opportunity when the incident took place.
He told EDP24.co.uk: ‘It is not important what I think.
‘I accept the decision. It is up to the referee.
‘My feeling is he already had the red card in his hand before he blew the whistle.
‘He seemed not unhappy to show this card. I watched it back since and we will analyse it with my players.
‘The behaviour in the lead up to this situation could be better.
‘It wasn’t necessary to take a foul.
‘Also I got the feeling the Portsmouth player put it too far away from his feet and there was no chance for him to reach the ball.
‘Perhaps it was a tactical foul and in which case a yellow card.
‘Not a big 100 per cent chance for me because Michael McGovern would be able to get the ball. I am not the referee. We have to accept what he thinks.’
Farke made eight changes for the game with the Canaries involved in the race to reach the Premier league and admitted is was a risk which backfired.
He added: ‘It is really sad.
‘We got the feeling we took a lot of risk in this game.
‘We had five players in the starting line up who had not been involved at the start since August. Grant had some under-23s games and 20 minutes at Bristol but he needs minutes to help his decision-making on the pitch.
‘The red card is perhaps a good sign why at centre back it is so important to get a feeling for distance.
‘You can get back fit but you need this time on the pitch so I would prefer he had 90 minutes here. Then it was difficult to play a side on fire.’