Liverpool defender Jeremie Frimpong will be ruled out until after the September international break.
That means the Dutch defender - who limped off during the Premier League opener against Bournemouth - will miss Liverpool's crucial games against Newcastle on Monday, and Arsenal on the following Sunday. Both games are live on Sky Sports.
"The medical team was completely right about Jeremie, to tell me I had to take him off because he's out until the end of the international break.
"I think I got criticised a bit by taking him off. [The medical staff] felt he had an issue in his hamstring. Good call to take him off otherwise he might have been out for longer. We expect to have him back after the international break."
Conor Bradley is also currently out injured - but Slot said he returned to training with the first team on Thursday. Joe Gomez is another right-back option in the squad.
"Conor played for a few minutes with us today, for the first time," said Slot.