Ospreys coach Lyn Jones believes it may be impossible to catch Gloucester in Pool 2 even if the Welsh team win the return match at the Liberty Stadium.
The Ospreys travel to Ravenhill hoping to repeat their bonus point win against Ulster last weekend, while Gloucester entertain Bourgoin having won away in France last week to maintain their unbeaten record in the group.
As Gloucester also have a home game left against Ulster, Jones fears they may set a target that cannot be reached even if the Ospreys win all three remaining games.
"Sometimes you can just sense with some team when it is going to be their year - Llanelli had that last year and nothing has gone right for them this year and Gloucester have had the ball bouncing their way and have reaped the rewards to be sitting pretty at the moment," admitted Jones.
"If you are a betting man then with Bourgoin and Ulster at home they are going to get to a minimum of 23-24 points and we have nine points. Three wins will give us 21 points which is one more than last year and nine times out of ten will get you through to the next round.
"However we have got to go to Ulster and Bourgoin and they will be difficult.
"These back to back games can be intimidating because people can quickly put things right.
"However last week we scored 48 excellent points against a determined Ulster team who are hard to break down and we appreciate how hard we need to work again on Friday to get what we want.
"People are underestimating Ulster. We know they are at the bottom of their game at the moment but they have a lot of quality players.
"We have to back our off-loading game because while it can go wrong at times it can also be unmarkable.
"As I mentioned, Ulster are at the bottom of their game but they will still fill Ravenhill and they can be loud and very supportive.
"There are a number of grounds you do enjoy going to and Ravenhill is one of those just because it a pure rugby place and the crowd are very appreciative."