Ulster face buoyant Stade Francais at Ravenhill on Friday night with coach Alan Solomons declaring "it is an uphill struggle for us now."
Defeat at Gwent Dragons in Round 1 means the 1999 champions cannot afford to fail to make home advantage count against the Paris club.
"The teams we have to play are all of a very high quality - Stade Francais, Leicester Tigers and The Dragons," said Solomons.
"We still have to go away to Stade Francais and Leicester Tigers and those will be incredibly tough matches.
"Against Stade it will be a case of going back to basics because our set piece play against The Dragons was poor.
"But we still had opportunities to win it so you have to look at it like that - it just was not our day.
"Stade Francais are a star-studded side and it is going to be a massive step up for us physically ... we just cannot afford to play like we did against The Dragons."