(CNN)Liverpool faces possible expulsion from the English League Cup for fielding an ineligible player in last Wednesday's 2-0 third round victory over MK Dons.
Liverpool faces possible expulsion from the English League Cup
Reports have identified Spanish midfielder Pedro Chirivella, who came on as a second half substitute in the win, earning the European champion a high profile tie against Arsenal in the last 16 of the knockout tournament.
Chirivella, who was making his first appearance for Liverpool since May 2016, spent the second half of last season on loan at Spanish second division club Extremadura, which means he would have required new international clearance when he returned to his parent club in the summer.
Liverpool requested that in July but the process can only be completed with the Football Association's intervention and it is unclear if the necessary paperwork was in place.
The English Football League (EFL), which administers its cup competition, said it was "currently considering the matter," in a statement.
The EFL has a range of sanctions at its disposal, ranging from a fine to being thrown out of the competition.
Liverpool reacted to the reports by issuing its own statement.
"The club are aware of a potential administrative issue pertaining to one of our players," it said.
"We are working with the relevant authorities in order to establish the facts of the matter and will be making no further comment until this process is complete."
Now third-tier Sunderland breached similar rules in 2014 by fielding ineligible player Ji-Don Won in four English Premier League and a League Cup match, but it was determined the mistake was with the authorities so the club escaped with a fine.
Meanwhile, Liverpool's dream start to the Premier League season continued Saturday with a slightly fortuitous 1-0 win over promoted Sheffield United Saturday.
Georginio Wijnaldum's second half strike went through the legs of Dean Henderson, the home goalkeeper reacting in horror as it trickled into the net behind him.
Henderson made partial amends when he denied Mo Salah a second with a superb block, but the damage had been done.
It was Liverpool's seventh straight win from the start of the season and 16th overall, leaving Jurgen Klopp's men five points clear of reigning champion Manchester City, 3-1 winners at Everton in Saturday's late kick off.