The 24-year-old has been with the squad at Euxton since November in a bid to earn a contract.
When he started training with PNE, Diaby was in the latter stages of a two-year ban from football after testing positive for higenamine.
That suspension ended earlier this month and he is free to play again.
No decision has been taken yet by North End on Diaby’s future.
On the financial side, it is understood that they would have to free up space on the wage bill should they decide to offer him a contract.
Lilywhites manager Lowe also spoke recently of wanting to see Diaby in a reserve game before any decision is made.
North End reserves had been scheduled to play in the Central League on Tuesday against Huddersfield but the fixture was postponed due to the first team being in action at West Bromwich Albion.
Diaby was born in Senegal before moving to Spain with his family as a child. His early career was spent in Spanish and Italian football.
He played the 2018/19 season with Lokeren in Belgium, from there joining Barnsley in July 2019 on a four-year contract.
It was during Diaby’s first season at Oakwell that higenamine was found in a urine sample provided after a Championship game.
He was banned under the FA’s anti-doping rules but cleared of knowingly digesting a banned substance.
North End’s January transfer business is very much a balancing act when it comes to squad size and wages.
Jordan Storey and Adam O’Reilly going out on loan and the contribution to their wages made by Sheffield Wednesday and St Patrick’s respectively, helped finance the incoming loan of Cameron Archer from Aston Villa.
Jamie Thomas went to Halifax on loan on Tuesday but another departure would be needed for more business as things stand.
As a free agent, Diaby could sign outside of the parameters of the transfer window.
The January window closes on Monday night, with EFL clubs having to register their squads for league games by February 4.
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