Inverness are seeking further explanation over Danny Wilson's eligibility in their semi-final defeat by Hearts after failing to understand why he could play despite his outstanding Scottish Communities League Cup ban.
The on-loan Liverpool defender set up Michael Ngoo's goal in the at Easter Road before Hearts won on penalties to secure a League Cup final place.
Wilson played in the 2010 final for Rangers and was sent off for denying a goalscoring opportunity in a 1-0 victory over St Mirrens, sparking a one-match ban in the competition.
Wilson signed for Liverpool before Rangers began the defence of their trophy and left without serving the suspension.
Inverness were told on Monday that Wilson was eligible, and Hearts had checked this with the authorities before the game, but they are not yet satisfied by the explanations.
In a statement, the club said: "As a result of discussions that have taken place throughout (Monday) afternoon, the club will be seeking further details and an explanation on events surrounding this matter."
It is not clear when Wilson served any suspension for his dismissal, with the offence not serious enough to spark an automatic ban for Rangers' next league game.
Wilson made his Liverpool debut in the Anfield team's opening League Cup game of the 2010-11 season, a penalty shootout defeat in September against a Northampton team containing Inverness striker Billy McKay.
The Scottish Football Association explained that Wilson's suspension would have applied to his first available league match in England.
A spokesman said: "The player did have an outstanding one-match League Cup suspension when he left Rangers FC to go to Liverpool FC in 2010.
"When the International Transfer Certificate was issued to the FA, this suspension was notified to them, as per FIFA regulations.
"It was then for the FA to apply the suspension in accordance with their own rules.
"The FA does not operate competition specific disciplinary procedures so the suspension would have been served in Liverpool FC's opening league match of season 2010-11 against Arsenal FC (the player did not play in this match).
"There was no outstanding suspension notified to the Scottish FA when the ITC was issued for the player coming back to Scotland.
"Therefore the player was eligible to play in last Saturday's League Cup semi-final."