The 20-year-old is being linked with a move to League of Ireland Premier Division side St Patrick's Athletic.
St Pat's recently signed former PNE striker Eoin Doyle from Bolton Wanderers.
O'Reilly recently returned from a loan spell at Stalybridge Celtic and his chances of forcing his way into the North End side look slim.
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He was signed by PNE from Cork-based side Ringmahon Rangers as a teenager, doing a scholarship before signing professional.
His one first-team appearance came as a substitute against Aston Villa in December 2018, a game Ethan Walker also came off the bench in.
Last year, O'Reilly had a spell in the League of Ireland, playing on loan for Waterford.
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