Aaron Mokoena's 121st minute header sealed the win over Coventry after Stephen Wright gifted Pompey an equaliser with an 90th minute own goal. Leon Best had put the hosts ahead with a stunning goal but for once, Pompey got some luck.
Avram Grant had problems before the game as Younes Kaboul, Richard Hughes and Steve Finnan were all injured so Vanden Borre, Mullins and Mokoena replaced them, whilst David James wasn't quite fit enough to replace Asmir Begovic.
The situation was apparently that bad that Grant would only place six players on the bench, one of them being 19-year-old German defender Leonard Sowah.
To say our first half performance was dire would be an understatement as we created hardly any chances, couldn't pass the ball at all and had to spend most of the half defending.
Kevin-Prince Boateng's toe poke at Kieren Westwood was the only opportunity Pompey mustered and that was after Leon Best spectacularly gave Coventry the lead with a stunning strike.
The Sky Blues were the better side in the second half too, until Boateng was forced off with a limp and was replaced by John Utaka. Grant also brought on Angelos Basinas late on and all of a sudden Pompey looked a much better side.
Our players went forward with more purpose but couldn't find a breakthrough and I thought we'd have to be resigned to a third round but the Coventry skipper did what the Pompey players couldn't and put the ball into Westwood's net.
Basinas floated the ball into the penalty area and both Stephen Wright and Clinton Morrison went to head it away at the same time, despite nobody in a dark blue shirt being anywhere near them, and in the confusion Wright nodded the ball under the crossbar and into the net.
That goal was harsh on Coventry who had deserved the victory but worse was to come for the home support after an extra time that Pompey completely dominated.
Our players kept possession better, with Basinas pulling the strings, but Webber really should have put the game to bed earlier after Brown put him through one-on-one but he couldn't get that final touch on the ball.
Basinas had also put Utaka through but instead of poking the ball past Westwood the Nigerian tried to take it round the 'keeper and ended up having his shot cleared off the line.
But with a penalty shootout (and therefore imminent Pompey defeat) looming, Pompey won a corner in stoppage time of extra time and up popped an unmarked Mokoena to glance a header past Westwood and to inflict a cruel defeat on Coventry.
So, despite a poor (terrible in the first half) performance, I have to commend the Pompey players for their spirit because lesser men would have wilted and allowed Coventry to walk all over them.
I was quite impressed with Basinas' cameo performance and he has to be in with a shout of starting against Birmingham if Jamie O'Hara's loan spell can't be extended.
This result should also breed some confidence going into the next game against a team that are unbeaten in twelve. We might just have some hope now...
Pompey Player Ratings
Asmir Begovic: 6 - A couple of decent saves.
Anthony Vanden Borre: 6 - Awful first half but improved as the game went on.
Marc Wilson: 6 - Did a job.
Aaron Mokoena: 7 - Generally solid at the back and scored the crucial winner.
Hermann Hreidarsson: 5 - Poor passing.
Michael Brown: 6 - Put himself about to say the least.
Hayden Mullins: 5 - Didn't do himself any favours.
Papa Bouba Diop: 4 - Spent more time on the floor than on the ball.
Tommy Smith: 5 - Ran willingly but no attacking threat.
Kevin-Prince Boateng: 6 - Only creative spark until he limped off.
Frederic Piquionne: 5 - Constantly caught offside.
Angelos Basinas (Mullins 77): 7 - Dictated the midfield.
John Utaka (Boateng 56): 7 - Game changed in our favour when he came on.
Danny Webber (Smith 70): 5 - Wasted two great chances.