Liverpool suffer Salah blow in chase for Champions League
The Egypt forward was forced off at Anfield on Wednesday after scoring in Liverpool's 4-0 victory against Galatasary, which sealed their place in the quarter-finals of this year's Champions League.
In-form Salah, 33, has scored in three of his past four starts after an uncharacteristic lean spell.
"It's unusual," Slot said at his pre-match press conference on Friday. "As a result of that I think you can expect the outcome. So, (he's) not available for tomorrow."
Slot gave no timeframe for Salah's recovery.
"The good thing for Liverpool and for us is that we go to an international break," he said. "The bad thing for Egypt is that he can't go there.
"We are hoping also with what Mo has shown in the past that he can recover faster than other players might in similar situations because he takes such good care of his body. History has shown that he can be earlier back than some others.
"But it's only two weeks until we go again so let's hope in that period of time he can be back."
Salah, who is rarely absent through injury, is firmly back in the fold at Anfield after a dramatic fallout with Slot earlier in the season, when he was dropped for several games.
Despite his recent good form, the Egypt forward has scored just five Premier League goals this season, compared with 29 in Liverpool's title-winning campaign in 2024/25.
Slot, whose team dropped valuable points in a 1-1 draw against Tottenham last week, admitted his side were not sharp enough in attack.
"We're struggling to score goals," said the Dutchman. "Not that we don't score them, but with all the chances we create, it's unbelievable that we don't score, especially looking at the quality we have up front and throughout the whole team."
Liverpool are fifth in the Premier League, two points behind fourth-placed Aston Villa, with the top five teams almost certain to qualify for next season's Champions League.
Slot's men face Manchester City in the FA Cup quarter-finals on April 4 and will meet defending champions Paris Saint-Germain in the last eight of the Champions League.