Joe Gallen expects to see Pompey back to their impregnable best when they host Blackpool on Saturday.
An unusually sloppy defensive display saw them beaten at struggling Bristol Rovers earlier in the week.
The Blues still remain in fourth spot, although are now four points adrift of the automatic promotion places.
And assistant manager Gallen now wants to make sure the fundamentals are done properly at Fratton Park.
He said: “We’re back at home and it’s an opportunity for us to get a result, but you still have to pick out the positives and negatives from the last game.
“The main thing to look at is conceding three goals and we need to return to some basic, honest defending on Saturday.
“Since we’ve been at the club there have been numerous times when we’ve had a bad result and have been able to bounce back pretty quickly.
"We need to return to some basic, honest defending on Saturday."
“We’ll be looking to do that again, but Blackpool are no mugs. They’re a good side and are difficult to score against.
“So we’ll need to improve to make sure we keep a clean sheet, while also trying to create as many chances as we can.
“Our offensive ability in the final third is a big thing for us and that needs to be balanced off with getting the basics right.
“There have been some excellent performances at the back this season, particularly from Sean Raggett and Jack Whatmough. We want our centre-halves to be back to their best form.”
Blackpool have won three of their past four matches – including a 5-0 rout of Wigan – as they aim to close the gap on the play-off positions.
Gallen said: “They’ve only conceded 26 goals in the league this season, which is pretty good going, and also have attacking threats.
“They have also got a few games in hand and so I’m sure they’ll still be looking to get into the top six.”
Pompey have no new injury worries ahead of the Seasiders’ visit, although are still missing a couple of players.
Gallen said: “Everyone who was fit on Tuesday night is still available, with Michael Jacobs and Alex Bass still out.”