The Egyptian forward, who has been a talismanic presence for the Reds throughout the 2017-18 campaign, lasted less than half-an-hour in Kiev before being forced from the field.
After tangling with Madrid captain Sergio Ramos, Salah left the pitch in tears as his European dreams came crashing down before those of his team-mates followed on an evening to forget.
Klopp revealed afterwards that the 25-year-old had been taken to hospital for medical tests, with Liverpool and Egypt now waiting anxiously to discover the full severity of a shoulder problem.
The Reds boss told reporters in the wake of a 3-1 defeat: “It's a really serious injury and the shock of the boys was obvious. We dropped a bit too deep.
“He is in a hospital for an X-ray. I think it's either the collar bone or the shoulder itself. It doesn't look good. That's it.”
“It was very bad for Mo, for us and Egypt. That's part of the sport I don't like. Things like this can happen.”
Liverpool had started brightly against Madrid with Salah on the field, but their energy levels dipped as the game wore on and individual errors proved costly.
Klopp added: “I don't know what would have happened had Mo stayed on, but everybody saw first half-hour we played good football.”
Two howlers from Loris Karis ultimately cost the Reds dear, with the German goalkeeper putting in a nightmare performance.
He rolled the ball onto Karim Benzema’s boot for Madrid’s opener early in the second half, before allowing a speculative effort from Gareth Bale to slip through his grasp seven minutes from time.
Sandwiched between those efforts was a stunning overhead kick from the Blancos’ Wales international, with his introduction changing the course of the tie after a Sadio Mane goal had briefly offered Liverpool hope.