Director of rugby Richard Cockerill says Leicester will probably have to win all five remaining Heineken Cup games to reach the quarter-finals.
Tigers lost their Pool Two opener with Toulouse last Sunday and face a crucial home game against Ospreys this Sunday.
Cockerill told BBC East Midlands Today the defeat had to be put in context: "We have lost one game away from home against the Barcelona of rugby clubs.
"We still have five games to go but probably have to win all five."
The winners from the six pools progress into the knockout stages and will be joined by the top two best runners up.
And while Cockerill says there was no disgrace in losing to Toulouse and the criticism his side received was harsh, he says there is now no room for error.
"Toulouse are one of the strongest squads in European rugby but we thought we could go there and win, or get something from the game," he said.
"We played some good stuff and worked hard. The effort was enormous, but at the crucial times we have to make crucial decisions - and we didn't.
"It was away from home against a very good side and the weather was atrocious. You have to play the conditions and the team in front of you. To go to Toulouse and then try to outplay them is madness. You have to go and try to frustrate them and eke out the points.
"That's what we tried to do and for part of the game it worked pretty well. But just before half-time when we were three points up and were probably in control we overplayed. We turned the ball over and they score and the whole swing of the game goes their way.
"The whole thing started to get away from us. We have to learn. We have had a good debrief and have to understand how to play those big games away from home."
Cockerill is convinced there is no need to panic after one game.
"But people have to keep everything in context," he added. "We have played one of the biggest teams in Europe. You are not comparing apples with apples.
"You have to work through it and take a measured view. That's sport. Sometimes you lose."