AT the back-end of last year when Leinster were on the retreat from Castres with mockery ringing in their ears, who could've guessed where they'd end up six months later? But spurred on in part by the withering critique of Neil Francis of this parish, the chaps became champions.

How far Leinster's transformation from doubters to believers will carry them this time is uncertain. They open their Heineken Cup campaign against a vibrant London Irish at the RDS on Friday, and you wouldn't be putting what's left of your savings on a victory for the holders.

That has more to do with Leinster needing another season in the shake-up to prove themselves as genuine stayers in the tournament, rather than with the visitors' undoubted quality. No one sets foot on the RDS with quite the same trepidation as on Thomond Park. Not yet anyway.

In fact, Leinster unpredictability mirrors Heineken Cup unpredictability. Apart from the hardy annuals, Munster and Toulouse, you can never be too sure who will emerge and who will bomb. Notwithstanding the head-scratching that occurred when Leo Cullen and his teammates dug themselves out of a hole to eventually win the cup going away, last season saw an almost complete wipe-out by the French clubs with only Toulouse making it to the knock-out stages.

The head that wears the crown is also invariably uneasy. Leicester won back-to-back titles in 2001 and 2002, but as the 15th staging of Europe's premier club competition approaches, no one else has managed a successful defence.

Once again, the only certainty is that the tournament is an open one. If London Irish going for Leinster's jugular is not enough to whet your appetite, the French champions, Perpignan, are headed for Limerick, and Stade Francais will bring their box of tricks to Ravenhill.

All that is against a backdrop of Irish rugby's current rude state of health following the Grand Slam, the Churchill Cup victory and Munster's Magners League. "Leinster are on a massive high," said England centre, Jamie Noon, who will be part of Brive's return to the tournament in a demanding pool which also includes Llanelli. "The Heineken Cup last season, and their Ireland guys winning the Slam, they're at the top of the pile at the moment, and we'll be trying to throw everything at them."

On the face of it, Leinster appear to be stronger than last season. There is more cover both in the front and second rows, Jonny Sexton and Eoin Reddan have the look of a tidy half-back pairing, while Luke Fitzgerald, Rob Kearney and Jamie Heaslip will be better players for their Lions' experience. Add in the sheer brilliance and physicality of Brian O'Driscoll, who has to be a strong contender for the IRB Player of the Year award, and the champions are even more of a proposition.

If Michael Cheika insists that the players have to prove themselves again, he believes that with CJ van der Linde close to full fitness, Leinster are better equipped to handle the physicality of European competition. "We also have the experience from last season. We'd never been that far before, so obviously that's got to help your belief. We have a good, strong dressing-room, and as far as morale's concerned, it's better than it's ever been. We've become a tight group over the years."

While confidence, as well as a vastly-improved defence, will be critical to Leinster's fortunes, it's still hard to imagine what life will be like after Rocky Elsom. Not even Felipe Contepomi in all his years exerted the same pervasive influence on the pitch. Last season, the Australian was a colossus and his departure has left a gap that will prove impossible to plug.

The promising Kevin McLaughlin has had a shot at blindside, Nathan Hines can play there, and Sean O'Brien may well wind up there, but no matter how well all three perform, Leinster just won't be Leinster without Elsom.

"Look, Rocky's gone, his days are over. He did a fantastic job when he was here, but we haven't got him any more," says Cheika. "Everyone expected us to go out and get someone to replace him, but we felt he was an individual, and there was an opportunity to set our team up a bit differently this year. I'm relaxed about it, I'm quite happy with the way our young back-rowers have stepped up to the plate. There are times when you've got to go out and get players to do a job for you, other times you feel another player is ready to come through. It was a conscious decision in how we recruited."

As for Leinster's pool – the outcome of which London Irish coach, Toby Booth, believes is easier to predict than the "end of the economic downfall" – Cheika is familiar with his English Premiership rivals as well as Llanelli. "London Irish came here in the pre-season and put it right up to us. They're going to try to stick it to us again, and it'll be a matter of how much we want to beat them."

More recently, he travelled to France to run the rule over Brive. "Very aggressive, very direct, nasty crowd. It's a tough place to go when they get a head of steam up and their supporters get behind them."

Meanwhile, there is no respite for Ulster who have failed to reach the knock-out stages in every season since becoming the first Irish province to lift the trophy in 1999. Pitched in with Stade, Bath and Edinburgh, new coach Brian McLaughlin and his assistant Jeremy Davidson will have to go some to avoid finishing bottom of the pool.

If Munster are up against a greater concentration of quality in Perpignan and Northampton, there is the counterweight of being able to coast through the Treviso games. With less of a recruitment need than Leinster, Jean de Villiers is still a prized addition to the backline, and training will be like a battleground at times such is the competition for starting places.

Although the Perpignan captain, Nicolas Mas, has said that his teammates mustn't have an "inferiority complex" when they take on Munster, the French champions' coach Jacques Brunel suggests that whatever mindset the players adopt mightn't count for too much anyway.

"The Top 14 is our priority. The format of the Heineken Cup is too unpredictable, too complicated for us to say we're going to win it. Two matches, a break, two matches, and another small break, and two more matches. Northampton will be difficult to beat but, for us, Munster are the favourites."

Given the French ambivalence towards the tournament – with Bourgoin the poster boys – Brunel isn't engaging in some elaborate bluff to lull Munster into a false sense of security. Still, no matter how Perpignan fare in the opening three games, Tony McGahan, Paul O'Connell and the rest know only too well the sort of welcome that awaits them at the Stade Aime Giral in December.

Even Toulouse, who've blazed a trail in the competition, tend to cast a jaundiced eye at the whole thing as if there's some anti-French conspiracy afoot. Only last week their coach Guy Noves was claiming that Munster had Nigel Owens in their pockets during the 2008 final.

Last season was only the second time since the advent of the European Cup that no French club made it to the semi-finals. A more sustained challenge from the superb Clermont Auvergne, who pushed Munster right down to the wire at Thomond Park last year, should by rights be anticipated, but since they've now lost three French championship deciders in a row, you can guess where their guns will be trained. That said, the final is scheduled for Paris next May which should act as an incentive to Stade Francais in particular.

In the meantime, Leinster are readying themselves. "Obviously we haven't played a European game yet, but we haven't felt any second-season syndrome," says Cheika. "A lot of people didn't expect us to win last season, and they probably don't expect us to win this season either. We have a lot of belief in ourselves, but you lose a few games and people start to doubt again. It's a new slate, everyone's at zero."

There's no sense that the holders will fall from heroes to zero, but a second triumph is likely to be beyond them.

mjones@tribune.ie