The 33-year-old Egyptian was not in the starting line-up — a decision Slot attributed to form rather than fitness — and then watched from the bench as five substitutes were introduced ahead of him, including 18-year-old Trey Nyoni.
Salah had gone through a warm-up on the pitch after half-time, with Slot visibly instructing him to increase the intensity. The expectation from the stands was that he would be introduced.
He never was.
After the final whistle, Salah completed his warm-down on the Parc des Princes pitch and then encountered a live TV broadcast. Steven Gerrard, Steve McManaman and Laura Woods were waiting on TNT Sports.
He smiled. He shook hands. Then he made clear, without a word, that he had nothing to say — and walked straight back to the dressing room.
The contrast with December is striking. When Slot left Salah out for a trip to Leeds, the forward told media he had been "thrown under the bus" and that he had no relationship with his manager. The backlash was significant.
This time, nothing.
Liverpool fans on social media suggested Salah had deliberately held himself back, conscious of the storm those comments created.
The broader context makes the situation harder. Salah has managed only 10 goals in 35 appearances this season — well below the standards he set in previous years — and missed a penalty in last weekend's 4-0 FA Cup humiliation at Manchester City. He has confirmed he is leaving Liverpool at the end of the season.
Goals from Désiré Doué and Khvicha Kvaratskhelia gave PSG a comfortable first-leg advantage. Liverpool face a rescue act at Anfield on April 14.
Salah may yet play a part. Whether Slot trusts him with it is another matter entirely.