Liverpool manager Jurgen Klopp plans to take legal advice before deciding whether to select defender Joel Matip.
The Cameroonian's availability is uncertain due to his absence from the Africa Cup of Nations.
The Premier League club are still waiting for clarity from FIFA, which may yet open an investigation into Matip's non-participation at the tournament.
Klopp said he would need the help of lawyers before making a decision, with his team facing Plymouth Argyle in the FA Cup on Wednesday.
"Of course I need advice, I'm not a lawyer, but the decision is for me to make," he told UK newspapers.
"I could put him in the line-up, I don't think referee is going to say ‘stop, stop, you cannot go on the pitch'.
"We have had a lot of talks over the days and weeks. We've done transfers quicker than this.
"It's already long-term, but now it's getting really tense on our side. We've tried everything, but at the end I have to make the decision."
Among Klopp's concerns is the potential punishment, including expulsion from the cup, if Liverpool let Matip play.
"That's the next thing, we don't know," Klopp said.
"Most of the time in life you know if you do this, then you get this. But it's not 100 per cent clear what happens."
After their cup clash, Liverpool – third in the Premier League – visit Swansea City on Saturday.