Dan Tuohy has been ruled out of Ulster's Heineken Cup clash against Glasgow at Ravenhill tonight.
The Ireland lock is also likely to miss the final Pool 4 game away to Castres in two weeks’ time due to a troublesome calf injury, which flared up again during last week's Pro12 win over the Scarlets.
Coach Mark Anscombe is expected to bring in Ireland blindside Iain Henderson to partner Lewis Stevenson in the second-row, while Robbie Diack looks set to continue his impressive form of late in the No 6 jersey alongside skipper Chris Henry and Nick Williams in the back-row.
Meanwhile, Ulster are on target for a significant move up in the ERC Heineken Cup rankings.
The ERC ranking system rewards consistent performances at the highest level in the two European competitions over a four-year period.
Currently in tier two, Ulster — the Pool 4 leaders and last season's beaten finalists, of course — are within striking distance of top level status.
Pool winners are awarded four points, with those finishing second, third and four getting three, two and one respectively.
In addition, quarter-finalists get an extra one or two points depending on where they finish in the top eight. All four semi-finalists get two more, with both of the finalists being awarded a further two apiece.
The winners gain another two, which means performance in the Heineken Cup ranges from a possible 11 ranking points for the champions, down to a single point for a club finishing bottom of their pool.
With Clermont currently on course to top Pool 5, like Ulster they look set to move up from tier two to tier one of the rankings for the first time.
Fellow-French club Pool 6 leaders Toulon also could book themselves a place in tier one next season if they continue their impressive unbeaten run.
But Cardiff Blues — bottom of Pool 6 — have a battle on their hands if they are to retain their top-flight status for next season’s pool-stage draw.
Both Ulster and Castres Olympique, the Pool 4 rivals who play Glasgow Warriors (Ravenhill) and Northampton Saints (Franklin’s Gardens) respectively tomorrow night before facing each other next Saturday at Stade Pierre Antoine, have added an additional player to their Heineken Cup squads.
Wing Chris Cochrane — 24 years of age, 6ft tall and 13st 3lb — is Ulster’s replacement for the injured Chris Farrell.
Castres’ incoming player is teenage back row forward Mathieu Babillot who has replaced the now-deregistered Benjamin Desroche. Babillot is 6ft 3in and weighs 16st.