The Liverpool defender has not played a game since April.
Sakho had been hoping to make his comeback during this pre-season after UEFA's case against him for a doping violation was dismissed, but the Frenchman has suffered a setback in terms of his fitness.
Liverpool manager Jurgen Klopp is quoted saying: “Mama had a little issue with his Achilles when he was playing, one day on, one off, this kind of thing.
“When he had his little ‘break’ he used the time to have a little bit of treatment and that now means another three or four weeks before he can train again.
“There was no surgery, he is just not about to train at the moment. He has got some rehab of course and it’s not too good a situation for him, for us, everybody."
From the sounds of Klopp's timescale, some would think that he could be back in training before the start of the season, but it has been pretty clear that the Reds boss would like all of his players to undergo a full pre-season so they can hit the ground running.
It now looks highly likely that new signing Joel Matip will partner Dejan Lovren on the opening day of the season at Arsenal should they come through pre-season unscathed, meaning Sakho will have a fight on his hands to get regular first-team football.
It is a setback for Sakho who has not kicked a ball in anger since a 4-0 win over Everton in April, and he will have been keen to get back to playing football again given his exile.