Guy Whittingham has demanded Pompey shape up at set-pieces.
The Blues boss was left frustrated by the number of wasted opportunities at Mansfield.
That was particularly the case at corners.
A lack of dangerous deliveries was obvious as the Blues forced five corners in the first 15 minutes at Field Mill.
Those set-pieces were all comfortably dealt with by the home side’s defence.
After paying plenty of attention to corners in training it was a source of irritation for the Pompey manager.
He is determined to put that right and will ensure the players will continue to work on corners ahead of the meeting with Chesterfield.
Whittingham said; ‘Our set-plays were disappointing at Mansfield.
‘Our first five corners were easily dealt with by them.
‘That’s something we work on week-in, week-out and they are worked on hard in training.
‘Jed didn’t put decent crosses in and one or two other things we’ve worked on in training didn’t happen either.
‘But we’ll keep practising and be determined to get it right.
‘Some people think it’s something we don’t work on – but, believe me, it is.’
Whittingham also chose to tinker with his back four at Mansfield.
He handed Bondz N’Gala his first start and switched Joe Devera to right-back to give Pompey’s defence more height and physical presence.
The Blues boss has previously indicated he likes to use full-backs with plenty of attacking intent.
He stated the selection manoeuvre at Mansfield does not mark a change in philosophy from him.
Whittingham was pleased with large parts of the attacking play despite that move last weekend.
He said: ‘We have to look at every opposition differently.
‘We sometimes have to go away and be hard to beat.
‘We were depressed after Mansfield but we went there and didn’t lose – so it’s not that bad.
‘We have good attacking players in the team who can hold the ball up, pass and dribble.
‘We have to keep doing it for 90 minutes, though.’