Ulster captain Johann Muller suffered a calf injury during the province’s 39- 21 RaboDirect PRO12 victory over the Cardiff Blues at Ravenhill last Friday night.
A scan today revealed that Johann Muller has a torn calf muscle and he is expected to be out of action for four to six weeks.
Speaking in the aftermath of the Cardiff game, Ulster head coach Mark Anscombe said: “Johann, at this stage, I’d say is pretty doubtful. He won’t be around next weekend and with Dan (Tuohy) going (into camp with Ireland), that hurts us a bit
“But Lewis (Stevenson) came on and did a good job and we’re fortunate to have someone of his capabilities and experience. Now we’ve just got to find someone else to lock up with him next week.”