The on-loan midfielder faces possible Wembley heartache, however, with the Blues drawn against Spurs or Fulham.
If parent club Spurs were to defeat the Cottagers in their quarter-final replay, it would mean O'Hara is Cup-tied for the eagerly-anticipated return to English football's HQ.
On Saturday O'Hara was his usual influential self – and was quick to have a quiet word at half-time with Piquionne following a less-than-impressive first 45 minutes from the French striker.
And after the impromptu pep talk, Piquionne was transformed from the moody forward who struggled to get into the game into a fearsome striker who netted the goals that took Pompey through.
O'Hara said: 'He was a different player in the second half. We had to get on his case a little bit in the first half and we had a few words with him at half-time.
'We told him to relax a bit because maybe he was a bit nervous. As the front man, he knows it's up to him to provide the goals, but we told him to play his normal game and it would come.
'But I think it got through to him because he was a totally different player in the second half.
'With Fred, he can go in and out of games at times. He looked a bit lost in that first half. There is a lot of responsibility on him to score goals playing that lone-striker's role.
'I just said to him "go out there, play your own game and show everyone what you can do". The centre-backs couldn't handle him in the second half when he turned it on. He looked fantastic.
'He poached the first one and the second goal was a fantastic finish. When he's on form and he's up for it, he's a great striker.'
Piquionne was in the right place at the right time to poke home from a yard for the opener, but his second was a goal of genuine quality as he latched on to O'Hara's pass and created the opening to fire home.
But O'Hara admitted that Pompey enjoyed a long overdue slice of good fortune as Liam Ridgewell's header – that replays showed had clearly crossed the line – was ruled out when Birmingham could have found a way back into the contest.
O'Hara smiled: 'I was standing on the other post and it looked like it hit the net! But you know what – who cares?
'I've seen the replay – but at the end of the day, I think we deserve a bit of luck considering all the stuff that has gone on this season.
'With everything that's gone on at the club, it's a bit crazy that we're going to Wembley. But I think we deserve it.'
Considering he is only on loan, O'Hara has clearly been bitten by the Pompey bug in his short time at Fratton Park.
He said: 'You can't not get wrapped up in it. It's a fantastic club and the fans are magic. They were unbelievable again.
'You would think that we're playing in an 80,000-seater stadium sometimes with the noise they make.
'It's just fantastic to give something back to them.'
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