Nyron Nosworthy and Cole Kpekawa will take time to show their full worth, according to Andy Awford.
The loan duo were both handed debuts in a revamped Pompey defence as they lost 1-0 at AFC Wimbledon.
The understanding will get better the more they playAndy Awford
Experienced defender Nosworthy came in for the injured Jack Whatmough, while the 18-year-old Kpekawa replaced Dan Butler at left wing-back.
There was also another defensive change with Ben Chorley preferred to Adam Webster.
Although the new pair had just one training session with their new team-mates, Awford felt it was the right way to go.
And the Blues boss believes they will both get better with more time to adapt to their new surroundings.
Awford said: ‘Nyron will be a lot better for the game and he will improve. It’s been a little while since he’s played but he used his experience.
‘We’ve had one day to work with them. They arrived on Thursday and we only had one training session so you can’t do too much work.
‘We will have a good week and we will be ready to go again against Shrewsbury.
‘The understanding will get better the more they play.’
Kpekawa looked like he might not even make his debut after injuring his back in the warm-up.
Awford said: ‘His back stiffened up a little but he was fine after some manipulation from the physio.
‘We’ve got the option to play him in a few positions and this time we chose the wing-back role.
‘It’s his first game for a while in senior football and he will get used to how we want to play.’