Ulster have suffered further injury setbacks to their back division ahead of Saturday's Pro14 match against Munster at Thomond Park.
Louis Ludik sustained a concussion in last weekend's win over Zebre and is following the return to play protocols.
Ulster say Will Addison sustained a shoulder injury in the same game, and his fitness to play this weekend will be monitored during the week.
James Hume is set to be out for around four months after having surgery.
The centre had surgery last week to repair a torn hamstring and faces a lengthy spell sidelines.
Hume lasted 40 seconds of the home win over Cardiff Blues before suffering a hamstring injury.
Another centre, Stuart McCloskey, has not played since suffering a shoulder injury in the win over Southern Kings in South Africa in his first game of the season.
Ulster reported on Tuesday however that the Ireland international has trained well and are hopeful about his fitness for the interpro game with Munster.
Ulster's 22-7 victory over Zebre last weekend saw them lie second behind Leinster in Conference A while Munster top Conference B, one point ahead of Irish interprovincial rivals Connacht.