Ulster have been sensationally rocked by a huge injury blow with Iain Henderson's season effectively ended by a significant hamstring tear.
The star forward sustained the damage against Edinburgh last weekend with director of rugby Les Kiss admitting yesterday that it would see him on the sidelines for up to six months.
While more details of his recovery period will be known after a consultation with a surgeon this week, such an absence would result in him missing the rest of the campaign with only faint hope remaining that he could feature during the tail end of the season.
It had initially been hoped that the 23-year-old could return in time for the Six Nations in February but he later said himself that he "isn't optimistic" about featuring in Ireland's attempt to secure a third title in a row.
Kiss then revealed that the typical timeframe for such a terrible injury would see him out until the season's conclusion at the end of May.
"The type of injury historically has been up to six months," said a dejected Kiss. "It doesn't look good in terms of the Six Nations."
Ulster are already without Tommy Bowe, Jared Payne and Stuart Olding for their must-win Champions Cup clash with Toulouse at Kingspan Stadium on Friday night but in the last week they have now lost Henderson, Darren Cave, Dan Tuohy and Peter Nelson to injury.
Having opened Pool 1 with a home loss to Saracens, the province know they cannot afford another defeat this weekend if they are to have any hope of making the quarter-finals.