Pompey are running out of time to ensure their League One campaign is extended beyond the first week of May.
A run of three successive draws means they are six points adrift of the final play-off spot with four games left to play.
It has still been a remarkable climb considering how far off the pace the Blues were when John Mousinho was appointed towards the end of January.
But Reeco Hackett knows they need to improve their attacking play to secure a return to winning ways at Oxford on Tuesday night.
He said: “It’s been frustrating and we’ve had a few draws that should have been wins, although I don’t think we deserved one on Saturday.
“We just haven’t had that cutting edge needed to break teams down and be able to run away with games.
“So we’ve let ourselves down because we want to go out there and do better – especially when we’re only a few points outside the play-offs.
"We were nowhere near the top six at the midway point of the season, so to still be in with a chance shows we’ve done well, although it’s going to be tough now."
“The manager has come in and all the boys have really bought in to the way he wants us to play and there has been an improvement.
“It might not look like that from the past few games, but if you take all the results from when he arrived then it’s been decent.
“We were nowhere near the top six at the midway point of the season, so to still be in with a chance shows we’ve done well, although it’s going to be tough now.”
Hackett’s tally of six goals for Pompey this term has only been bettered by Colby Bishop and Ronan Curtis, but the forward is not satisfied with his overall contribution.
He said: “I haven’t played as much as I would like and haven’t been amazing when I have got out on the pitch.
“I don’t think I’ve scored enough goals and would describe it as average. I would expect more from myself and need to be more clinical.
“Perhaps I’ve played it a bit safe at times or perhaps I need to be a bit more selfish – it’s up to me to produce a higher standard.”