The former Manchester United player did not make PNE’s 25-man squad and has not featured in the Central League or Lancashire Cup games this season.
His only involvement in the squad for a competitive game so far this campaign was as an unused substitute in the first round of the Carabao Cup at Mansfield.
North End head coach Frankie McAvoy has revealed that an injury has kept Harrop off the training pitch and out of the reserves matches.
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But he hopes it will not be long before the 25-year-old is able to re-join training.
McAvoy said: “Josh is injured, he’s got an issue with his knee which has taken a bit of time to clear up.
“Hopefully he won’t be too far away. He’s been out on the grass a few times but it’s a niggling injury which he needs to get sorted.”
Harrop last played in the PNE first team on Boxing Day last year, coming on as a sub in the 1-0 win over Derby.
He then spent the second half of the season on loan at Ipswich Town. In September when PNE registered their senior squad with the EFL for league games, Harrop was not included – nor were Paul Huntington, Joe Rafferty, Jamie Thomas and Connor Ripley.
Huntington and Rafferty have since been registered, with Thomas keeping up his match fitness in the reserves.
Goalkeeper Ripley is with Salford City at the moment as an emergency loan.
He joined the Ammies for an initial seven-day loan on October 16 when they lost goalkeeper Tom King to injury.
That has since been extended and Ripley has played four times.
On the injury front, North End are hoping to have Ched Evans back after the international break.
It has been a long absence for the Welsh striker who has not played in the first team since August 17.
And the forthcoming gap in the fixture list should see him resume training.
Evans has been suffering from plantar fasciitis, a painful injury to the tissue in the bottom of the foot.
That has led to a couple of other niggling injuries but there appears to be light at the end of the tunnel now.
McAvoy said: “Ched is back up, he’s done quite a good bit of running. The next game will be too early but after that we hope to have him back.”