Salah, ahead of facing Fulham today, hasn't scored in the past three games.
But Slot said: “I think Mo has smiled less because we went out of the Champions League and we lost the final. It has nothing to do with not scoring a goal.
“For me it’s simple, sometimes the fixture list is more difficult than other periods of the season so you face Paris St Germain, Newcastle in a final and then a derby.
“He hasn’t scored in three - so that’s why he has to score on Sunday! Hopefully he will. Paris St Germain is one of the best teams in Europe at the moment.
"Newcastle in the final - they were all over it. Everton, with 10 people in their own 18-yard box all the time, it’s so difficult to score a goal against them.
"I know Mo - and he lives for goals. It would be weird if he was saying ‘oh, I’m happy I didn’t score.’ But he’s not distracted or thinking 'I can’t play football any more'. Mo knows that his biggest quality is he can play a poor game and still score a goal. So his head is not all over the place. Not at all.
"That’s why he scores so many goals, because he wants it so much. There were probably periods this season when he smiled a bit more - but that’s not just him."