Kenny Jackett has denied Pompey are focusing their transfer window attention on the loan market.
But the Blues boss conceded clubs are faced with difficulties in securing permanent deals during January.
Signing players permanently is a lot easier in the summer. To sign players permanently in the January window is very difficultKenny Jackett
Anton Walkes has become Pompey’s third recruit of the window following his arrival from Spurs.
He joins Wolves pair Connor Ronan and Sylvain Deslandes moving to Fratton Park on loan deals.
And Jackett is still pursuing Derby midfielder Jamie Hanson on a temporary basis for the remainder of the season.
There are loan alternatives should Derby’s injury situation ensure he cannot depart the Championship club.
And, as the transfer window enters its final day, Pompey continue to dip into the loan market.
Jackett said: ‘We are not purely looking at loans, if there are permanents there then it is fine, but it’s quite a hard one to do.
‘Where you may sign a permanent player in the summer, it might be a small fee, it might be a free transfer because they are out of contract or just somebody perhaps with a year left that sides are looking to trade.
‘Regardless, signing players permanently is a lot easier in the summer. To sign players permanently in the January window is very difficult.
‘It is quite a short window. However, between now and May 5, in terms of bringing someone in and having a look at them, it is ideal.
‘Whereas the first transfer window is a lot longer.
‘With a lot of clubs there are mainly loans in terms of players, younger players coming in. These are younger players you want to look at to try to build.
‘If you maybe take four younger players and end up signing two of them, they could go on to be really good players.’
Pompey’s chances of recruiting ahead of today’s 11pm deadline will be influenced by outgoings.
Kyle Bennett remains the obvious choice, having been unused from the bench in six of his last seven inclusions.
There has already been interest from a League Two side over a loan deal.
Kal Naismith is another, with his contract up in the summer and clubs also monitoring his availability.
In the meantime, Wigan are reportedly interested in the Scot, who has started the last three matches following injury.
Walkes has already arrived this week on loan – but Pompey are in the market for more.