Keyman Iain Henderson is unlikely to play for Ulster again this year and could be in a race against time to prove his fitness for Ireland's first Six Nations contest of the year in February.
The 23-year-old had only returned from a hand injury sustained during the World Cup two weeks ago but was carted from the field during Ulster's Guinness Pro12 win over Edinburgh on Friday night with a hamstring issue in his left leg. He will undergo a scan today.
Definitely out of Ulster's Champions Cup double-header with Toulouse and the Pro12 trip to high-flying Connacht on Boxing Day, Ireland boss Joe Schmidt will hope to see the powerful forward return during January in order to rack up some game time before the Six Nations begins with the visit of Wales to Dublin on February 7. After his star turn at the World Cup, Henderson figures to be an important piece of the Test side's pack.
While Ulster's win over Edinburgh lifted the province back into 5th place in the league table, the victory came at a huge cost with Henderson not the only injury problem ahead of the must-win hosting of Toulouse on Friday.
Darren Cave was also forced off early with a sprained AC joint in his shoulder while Pete Nelson sustained what was described as a nasty foot injury and Dan Tuohy damaged his ankle. The full extent of those injuries are expected to be revealed today.
There was better news on Rob Herring with the hooker said to be fine despite limping badly in the final minutes of Ulster's fourth win of the season.