The full-back was substituted after 25 minutes at Anfield having picked up an issue and will now be assessed by the club's medical team.
"It's difficult to say how serious it is, but it's always serious if a player goes out in the first half," Slot told his post-match press conference. "Not because I didn't like him, but because he asked for it himself.
"He didn't ask for it because he was tired, he asked for it because he felt something.
"That's first of all not a good sign, but it is always difficult so close after the game to tell you exactly what it is. Let's wait and see.
"I would be surprised if we will see him playing for the England national team this week, but hopefully he can."
