Michael Appleton has pledged not to gamble on Luke Varney’s fitness.
Pompey’s joint-top scorer has missed the past two matches with a medial knee ligament strain.
He sustained the injury at Burnley on his first start following a hamstring problem.
Varney is rated as 50/50 to make the New Year’s Eve trip to Leicester.
The 29-year-old is desperate to face the club he supported as a boy and where he started his footballing career.
But Appleton is wary over rushing the forward back too early.
He fears doing so could potentially rule the former Crewe man out of action for an even longer time frame.
And Pompey’s manager has pledged to take his time before letting Varney return.
Appleton said: ‘Luke is 50/50 to make the Leicester game at this moment in time.
‘The type of character he is, he is desperate to do everything quicker than he should do.
‘We have had to put the reins on him a couple of times in the past week alone.
‘He has had an injection and needs to quicken things up but seems to have responded quite well.
‘He is a big, big player for us – a massive player – and if we can get him back in the squad it gives everyone a boost.
‘What he does is causes a threat to defenders in behind with his pace.
‘If we get him back for Leicester, fantastic.
‘If not, we have to make sure we look after him properly so we don’t lose him for an amount of time.’
Varney has scored five goals in 17 appearances since his summer move from Derby.