Iain Henderson was only back from a hand injury.
Ulster beat Edinburgh 14-7 last night but they suffered a number of injury blows, leaving them in danger of going into their Champions Cup double-header dangerously understrength.
Les Kiss' side lost Henderson, Darren Cave, Peter Nelson and Dan Tuohy to injury while Franco van der Merwe was also taken off at a rain-soaked Kingspan Stadium.
The most worrying of all the blows was that to Henderson, who started as blindside flanker.
With just four minutes on the clock, Henderson pulled up trying to chase down a Nick Williams block-down and, after a break in play for treatment, was carted off.
Ulster face Toulouse in back-to-back Champions Cup games next and the Ireland international may well miss out on the fixtures.
Post-match, Kiss told
BBC that it was too early to tell the extent of the injuries to his quartet. Henderson will go for a scan within the next 24 hours to learn the extent of his injury.
Any serious ligament damage could see the 23-year-old in danger of missing the start of Ireland's Six Nations.
Nelson and Cave were taken off after shipping heavy blows. Tuohy was felled in the second half as he fell awkwardly from a line-out and was left clutching his ankle.
Clive Ross was forced to pitch in as second row having earlier been called up for Roger Wilson [back spasm] and placed on the bench.
