Livorno have lost Ibrahima Mbaye for a month after he was diagnosed with a groin strain.
The Senegalese 19-year-old was visibly in pain at the end of the 2-2 draw with Inter, his parent club, on Monday evening.
Medics have now confirmed the left-back suffered a groin strain with a lesion and will be out of action for at least four weeks.
It is a heavy blow to the Amaranto in their bid to escape relegation from Serie A.
Emerson also suffered an injury in the same match and will be sidelined for three weeks.