Table-topping Luton are the only side to have scored more League One goals for Pompey so far this season.
Kenny Jackett’s side have netted nine in their past three games – and 64 in total – to ensure they remain in the promotion hunt.
But their form in the first half of the campaign was also built on defensive solidity, something that has not been quite so apparent in recent weeks.
And ahead of Saturday’s clash with Scunthorpe at Fratton Park, Jackett wants to ensure they remain competitive at both ends of the pitch.
The Blues boss said: “We’re the second top scorers in the league – behind Luton and level with Barnsley. That’s pretty good.
“Where we’ve struggled recently is defensively – we’ve conceded too many goals. We’re joint seventh there and you wouldn’t have thought that if you’d seen us up until Christmas.
"We know we can do well at this level and have proved that this season – we’ve been competitive even in the games we’ve lost.
“I don’t want to take away the intent to get forward and win games, but there has to be a balance. You give yourself problems if you don’t keep the back door shut.
“We know we can do well at this level and have proved that this season – we’ve been competitive even in the games we’ve lost.
“There’s a degree of confidence, but you obviously have to keep working on that because a high standard is needed to keep pace with the sides at the top.
“If it’s only nine games in then you don’t worry too much about what other teams do, but we’ve got direct competition now.
“There’s nothing you can do about them, however, and can only have an effect on your own performances. We need to keep up our end of the bargain.”
Pompey face a Scunthorpe outfit sitting 15th in the table, but just four points clear of the relegation places.
Jackett said: “They’ve got a good squad of players and a very experienced manager – they have been a play-off side before this season.
“Like a lot of sides in the bottom half of the table, they’ll be wanting to get points on the board to keep them away from danger.”
Ronan Curtis will miss out again for Pompey after severely damaging his finger when it was caught in a door.
Jackett explained: “It was quite a bad one. It was hanging off and had to be sewn back on. The plastic surgeon did a very good job.
“He won’t be playing on Saturday and the estimation is between two and six weeks. He’ll see a specialist on Friday and that report will also be sent to the Irish medical team.
“James Vaughan has felt his back and I don’t know whether he’ll be fit, while we’ll hoping Andy Cannon and Bryn Morris will be back within a fortnight.”