Steve Cotterill pointed to Pompey's lack of squad depth as the cause of their late collapse at Nottingham Forest and conceded: It's killing us.
The Blues boss cut a dejected figure in the post-match press conference after seeing his side crash to a 2-1 defeat having led the game up until the 87th minute through Kanu's classy opener.
But an own goal from Ibrahima Sonko and Marcus Tudgay's stoppage-time clin-cher sent Pompey spinning to a morale-sapping defeat.
The Blues are now looking over their shoulders at the relegation battle, rather than casting an eye towards the play-off places.
Cotterill said: 'Unfortunately what we are doing is wasting games because it's very, very difficult with what we have got in this league.
'This is a proper league and it's very, very difficult to win games.
'To see games out in the Championship is very tough.
'It's very demanding because, game after game after game, it's very relentless and you need a squad.
'If we had their substitutes' bench, we would have won the game – 100-per-cent.
'But this isn't the first time it is killing us, it has killed us over the Christmas period and it killed us the first seven games of the season.
'That's why we were bottom of the league.
'We had a very, very lucky purple patch where we have managed to put out the same 11 players game after game but we also had a few Saturday-to-Saturday games that allowed knocks and niggles to clear up and confidence to stay high.'
Rookie Tom Kilbey was asked to play as a makeshift striker for the final 20 minutes. Cotterill had no ready-made replacements for either John Utaka or Kanu, below, as Pompey sat deeper and deeper before switching to five at the back in an attempt to see the game out.
Cotterill said: 'John Utaka tweaked his hamstring and Kanu was on his last legs.
'But we weren't able to put a striker on instead of them.
'It's difficult because it was Tom Kilbey, who is a million miles away from trying to play in our team.
'Have a look at their bench and see who they bring on.
'Had we been able to do that, we would have seen the game out, for sure.'
With on-loan defender Ritchie de Laet having made an impressive debut at right-back, Cotterill is now hopeful he will be able to bring in some more new blood during the remainder of the transfer window.
He said: 'There have been a lot of phone calls to see if we can try to get players in and it's not an easy job.
'There have been lots of late nights hoping that things come across the line for you.
'The chief executive is trying to get some bodies in at the moment – that's with him.
'I've spoken to a couple of managers and we will be trying to do it with a few bargains.'
Asked when he would be speaking to Blues owner Balram Chainrai, Cotterill replied: 'I don't know. I don't expect anything, I just get on with my job.'