Colchester United expect defender Nico Lawrence to be out for several months with ankle ligament damage.
The 19-year-old centre-back is on a season-long loan from Southampton but limped off in the first half of Saturday's 3-0 win at Gillingham.
U's boss Ben Garner told the club website: "It is going to be months rather than weeks - it's a blow.
"We are speaking to Southampton, obviously as he's their player, about what's best for Nico and his recovery."
In better news, fellow central defender Tom Dallison is expected to be back in action towards the end of September.