The 23-year-old, on loan from Tottenham Hotspur, has had his share of disappointment at the famous stadium and is desperate to end his stint at the relegated south coast club against Premier League champions Chelsea.
O'Hara, Portsmouth's most impressive player this season and the fans' favourite, has a double stress fracture in his lower back and faces a battle to recover for the showpiece.
"I have a big decision to make before the end of the week because there is a risk of a long-term injury," O'Hara told reporters at the Portsmouth's training ground on Monday.
"I know it's a massive game and I'm desperate to play but I also would not want to jeopardise the team's chances if I'm not fully fit.
"Any other time of the season it would just be a case of rest and possibly eight weeks out."
O'Hara reached two League Cup finals with Tottenham. He did not get on the pitch in the victory against Chelsea in 2008 despite playing in the earlier rounds and a year later had his spot-kick saved by Ben Foster as Manchester United won a penalty shootout.
This season he had to sit out the FA Cup semi-final at Wembley because Portsmouth played Tottenham.
O'Hara ruffled a few feathers at the north London club, for whom he signed a new contract this season, saying he hoped they lost so that he could play in the final.
Now, however, injury threatens to scupper his big day.
"I'll have an injection tomorrow and see if it settles down in which case I would be okay to play but I will sit down with the manager and make a decision," he said.
"I have been speaking to the doctors back at Spurs and they haven't been trying to stop me playing in any way. They just want me back for pre-season."
With Portsmouth preparing a huge clear-out of players to tackle their spiralling debts, O'Hara will not be at Fratton Park next season and his future remains uncertain.
"After this game I'm back at Spurs. I will have to sit down with Harry Redknapp and see what he wants to do," he said.
"I wouldn't want to go back to sit on the bench and play one in six because I've enjoyed playing regularly at Pompey and being a big part of the team.
"Personally I've had a great season down here and I hope it's a stepping stone to go on to better things."
