Firmino suffered an abrasion to the cornea in his left eye after a clash with Jan Vertonghen during their victory over Tottenham over the weekend and was a doubt for Tuesday's Group C opener in the Champions League.
However, the Brazilian netted a late winner from the penalty spot after coming on as a second-half substitute.
And Mane has seemingly joked that his strike partners knack for look-away passes and goals proves he only needs one during the game.
"I think Bobby doesn't need his eye to play so I told him," Mane told reporters after the game. "I sent him a message on Monday saying, 'Hey Bobby, come on, we need you'.
"You've all seen the 'no look' goals so I think he doesn't need his eye to play. I texted him saying, 'You don't need your eye'."
On the emphatic 3-2 victory at Anfield, the Senegal winger could not hide his delight.
"I think it's a big result (against PSG) honestly. It is very important for us to keep going on our good run," he said, as quoted by Sky Sports.
"It was not an easy game because PSG are one of the best teams in the world, but we played very well and deserved to win."