Pompey fans have been asked to show patience with Erik Huseklepp.
Steve Cotterill warned supporters their new £1.5m hitman needs time to flourish in the Championship.
Huseklepp made his highly-anticipated full debut against Cardiff City in Saturday’s 1-1 draw at Fratton Park.
But it was a disappointing display from the 26-year-old as he struggled to get involved in the game.
Huseklepp started up front before being moved to the left wing and was then subbed just after the hour mark.
Hopes are high the Norway international can have a big impact after his arrival from Italian club Bari earlier this month.
His impressive six-minute cameo in the recent draw with Bristol City got fans talking, but he was unable to build on that encouraging display.
Cotterill is confident Huseklepp will deliver for his side.
But he knows he needs time to settle into his new surroundings.
Cotterill said: ‘He’s only a young boy. He came on last week and all of a sudden he had dancing feet and he looked electric.
‘Then on Saturday, he had an average performance.
‘In the time he was on the pitch we were all very average, so he was no different to anybody else.
‘He will do fine for us once we get him settled in.
‘It’s going to take a while for him to bed him in.
‘We are not buying somebody else straight out of the Championship and all of a sudden they can drop in and know what English football is all about.
‘He was what he was on Saturday, but he will be fine.
‘We just need to give him time to bed in.
‘He’s ended up playing against a tough Cardiff team with probably two of the biggest, strongest centre halves in the league.
‘He’ll do okay when he beds in, he’ll do okay.
‘I’m trying to lower the expectation a bit and take some of the pressure off him.
‘We need him to flourish.’
Cotterill insists a strong dressing room spirit will help Huseklepp’s process of adapting to his new terrain.
He revealed he has already fitted in well with his new team-mates.
Cotterill said: ‘We’ve welcomed him and he has joined in with the banter straightaway.
‘A lot of it is aimed at him, anyway.
‘He’s come in to a good, solid dressing room and he’s been made to feel welcome.’