As a 19-year-old at Metz, he managed to catch the eye of Houllier, who had moved on to Austrian side Red Bull Salzburg, charged with discovering exciting new talent.
Houllier said: “I first saw him playing for Senegal in the 2012 London Olympics.
“What I liked straight away was his speed and ability on the ball. It was fantastic for a boy of his age. I had also seen him on French television.
“I quickly discovered that Metz would be willing to sell for financial reasons. Salzburg agreed to buy him and we paid £4million. The potential was there and we just had to make sure he was well looked after.
“When I was at Liverpool, I introduced a player liaison scheme where foreign players would be helped to settle into a new and strange environment. We did the same at Salzburg where shy Sadio joined a French-speaking family.
“We played a friendly against Bayern Munich and Salzburg won 3-0. He scored one and made one. Bayern wanted sign him after that."