Torquay have informed the Football League that an unregistered player took part in their game against Hereford on Tuesday night.
The Gulls handed debuts to Jake Robinson - on loan from Shrewsbury - and Craig Stanley, who recently joined the club from Morecambe on a temporary deal.
One of those two players was not eligible to play.
The club released a statement which read: "Torquay United have informed the Football League of an incident relating to Tuesday night's match with Hereford United at Plainmoor.
"The club was alerted to the fact an unregistered player had taken the field after kick-off and we have voluntarily offered our explanation to the Football League.
"We are now waiting for a response from the Football League and, as such, we will be unable to make any further comment at this time."