Iain Henderson faces a fitness battle to be ready for Ulster's Heineken Cup double header against Treviso.
Ulster have confirmed that the back-row forward will be out for up to six weeks after sustaining a toe ligament injury in Saturday's win over Montpellier.
Henderson is expected to miss four of Ulster's Pro12 games and Ireland's autumn international series.
He will target a return before the back-to-back Heineken Cup fixtures against Treviso on December 7 and 14.
Ulster, who are top of Pool 5 after victories over Leicester and Montpellier, first play the Italians at home on December 7.