England World Cup star Lewis Moody believes Leicester will require "a monumental effort" to launch their European Cup campaign with a win on Saturday.
Moody and the Tigers head to Dublin, where a Leinster side packed with players still bristling from Ireland's dismal World Cup campaign awaits them.
Although Edinburgh should provide a little light relief for Leicester next week, they then resume European Cup action in December with back-to-back games against triple European champions Toulouse.
With only one team likely to progress from Pool Six, wins on the road could decide who marches on and who bows out.
Moody said: "It is going to be an incredibly tough encounter against Leinster.
"We know all about the talent they have available, and it will take a monumental effort to come away with a win, let alone qualify from such a tough pool."
Moody and fellow World Cup players like Martin Corry and Ben Kay returned to domestic action when Leicester beat EDF Energy Cup opponents Cardiff Blues last weekend, as an impressive second-half performance confirmed the Tigers are stirring.
He added: "It obviously takes a bit of time for everything to gel again when you have so many people coming back from a long absence and some new faces in the squad.
"It usually takes me about a month to learn the new moves, so trying to remember the Leicester calls in 10 days was difficult.
"But it was really important for us to get some game-time together before such a big match as this one."
Leinster and Ireland captain Brian O'Driscoll admits there is little room for manoeuvre, given the pool's quality.
O'Driscoll said: "Lose your first game and the pressure is immediately on. The likelihood in this pool is lose two games and you will be out.
"I guess the message is, 'don't start slowly'."
Full-back Geordan Murphy makes his 50th Heineken Cup appearance for the Tigers, while centre Ollie Smith has recovered from a hamstring injury to partner Dan Hipkiss in midfield.
As head coach Stuart Lancaster polishes the axe he will soon wield over his World Cup training squad, Exeter Chiefs coach Rob Baxter has backed Jack Nowell, Henry Slade and Luke Cowan-Dickie to be given a stay of execution.
Italy Under-20s held off a late Samoa blitz to retain their place in the World Rugby U20 Championship on Saturday and head coach Alessandro Troncon believes the experience will have served as a valuable lesson for his young troops.