Angelo Ogbonna will miss a significant chunk of West Ham's season after picking up a serious knee injury against Liverpool.
The Hammers defeated the Reds 3-2 on Sunday to leapfrog Jurgen Klopp's side into third place in the Premier League table.
But the buoyant mood from that victory has been tempered by the discovery of an anterior cruciate ligament problem for defender Ogbonna.
The Italy international has already started recovery work on the injury to his right knee.
'After being substituted following a separate incident that led to him suffering a cut above his eye, Angelo felt some discomfort in his right knee so we scanned him to ascertain the extent of the injury,' said West Ham's head of medical Richard Collinge.