The winger is thought to have taken a heavy blow to the arm in the Reds' morning session at Melwood on Wednesday and was sent for scans at the Spire Liverpool Hospital to assess the extent of the damage.
He was pictured leaving the club's Melwood training base in a sling on Wednesday afternoon, having come back from the hospital, and drove home unaided.
If Liverpool's worst fears are confirmed, and Mane has dislocated his shoulder, he could require a lengthy period - potentially up to three to four months - to recover.
It would be a devastating blow to Jürgen Klopp, who was delighted with the impact the Senegal international made in their 4-3 win over Arsenal on Sunday - scoring a stunning individual goal to mark his competitive debut in style.
That followed a pre-season campaign in which Mane was regularly one of the stand-outs, his pace and directness as well as his defensive work-rate having made him a guaranteed starter for Burnley away and the coming league games to follow.
The 24-year-old offers different qualities to the Reds' other attacking midfielders, as well as allowing Klopp to utilise a fluid 4-3-3 which saw Mane thrive down the right-hand side, which allowed him to make such an excellent early impact.
Klopp potentially forced to consider system change if Mane's injury is revealed as serious
In Mane's absence, the German might be forced to tinker his system - with the other senior wide-man in the squad Lazar Markovic, facing an uncertain future, and youngster Sheyi Ojo out for a month with a back fracture.
Klopp could opt to revert to a familiar 4-2-3-1 formation, with Adam Lallana capable of playing on the right, while Georginio Wijnaldum or even Divock Origi are other possible options to take up the role.
But neither are particularly accustomed to playing wide right, with Wijnaldum's experience on the flanks having come on the opposite side and Origi preferring a traditional striking role.
It is likely that Klopp could switch back to such a set-up if Mane is ruled out for a prolonged period, particularly with Daniel Sturridge, Origi and Danny Ings competing with Firmino for the sole position as striker.
He will no doubt be assessing such options as Liverpool wait to hear more on Mane's injury, but nevertheless missing the Reds' new No.19 for any period of time would be a disappointing setback.
The day earlier, James Milner returned to training from an ankle problem while Daniel Sturridge is battling back towards full fitness after missing out on the squad at Arsenal because of a slight hip problem, from which he only returned to training on Friday.
Milner could be another potential option to replace Mane, if necessary, although it appears Klopp is keen on using the experienced Englishman as left-back over the questionable Alberto Moreno.
Academy midfielder Pedro Chirivella is also set to return to light training. The Spaniard featured in the Reds' first friendly at the start of July but missed the rest of their pre-season preparations with a quad injury.