Leam Richardson admitted Paul Jones’ first-team spot is his to lose after a successful re-emergence.
Pompey have yet to concede a goal since the 29-year-old was brought back into the side two games ago.
Following four clean sheets in eight outings on loan at Crawley, the keeper was recalled to replace the unavailable Ryan Fulton over the Easter period.
The Blues have since beaten Notts County and Carlisle to keep alive their automatic promotion aspirations.
Jones even earned the first-team nod ahead of Fulton in the 1-0 victory over the Cumbrians, following the youngster’s squad return.
And Richardson believes the former Exeter stopper’s displays are worthy of his Pompey selection.
The Blues’ assistant boss said: ‘It has been difficult to pick the side for a while.
‘Everybody is more or less fit, we have a good squad to choose from and I think the gaffer has sleepless nights over who to put on the bench let alone the starting XI!
‘Jonesie went out on loan to Crawley after injury to get his eye in and up to a level of fitness with a view to coming back to play.
‘The gaffer made that clear to him and thankfully he has come back and kept two clean sheets.
‘It was hard to choose who to play against Carlisle because you have two very good keepers, but the manager gets paid to make those decisions.
‘I think after two clean sheets it now has got to be Jonesie’s place to lose.
‘He has done very well, exactly what you expect.
‘Jonesie is a seasoned pro, a seasoned keeper, and you expect a level of performance from him. He is turning them in at the moment.’
Carlisle also represented the first time Jones has made successive appearances under Paul Cook.
He was initially overlooked in favour of Brian Murphy earlier in the season, only to suffer knee ligament damage in his first league start of the campaign.
That arrived in the 1-1 draw at Oxford United in September, with the keeper seeing out the match.
Murphy, Aaron McCarey and Fulton kept goal during Jones’ time on the sidelines.
Fulton certainly impressed Cook following his loan arrival from Liverpool, making 13 appearances.
However, following a call-up for Scotland under-21s at the end of last month, the 19-year-old is out of the starting XI.
Regardless, Fulton is on loan at Fratton Park for the remainder of the season.
And Richardson has been impressed with the youngster’s ongoing contribution.
He added: ‘Ryan has done well.
‘For a 19-year-old he is going to have a great career, unless something drastically goes wrong. Touch wood it doesn’t.
‘He is a bright kid, has a really good work ethic. Liverpool have some really good keepers at the minute – and Ryan is included in that.’