Leinster have 10 points from their four games and need to win their final two games – against the Llanelli Scarlets and Exeter Chiefs – with bonus points. But even then they are not guaranteed progression as they will be relying on results from other pools going in their favour.
"People have written us off now. We've been beaten by Clermont and are in a poor position to get through," said McFadden. "But it's still possible. And if we qualify from this group it will be one of our greatest achievements.
"It's still possible but unfortunately we've made it very difficult for ourselves by losing to Clermont.
"The pool is out of our control now. If we don't win our next two games with bonus points we're pretty much done. We just have to do our best and hopefully things will work in our favour."
For the immediate future, McFadden is determined to make the most of the opportunities for more regular game time he is being afforded at Leinster.
His natural pace makes him a fantastic option on the wing for both club and country. It's not his favoured position – "my favourite position is 12" – but when you bounce around positions as often as McFadden, having a regular berth is what's most important.
"I'd like to put myself in the shop window to be selected for the Six Nations," said McFadden. "For me, these games over Christmas and the next Heineken Cup pool games are very important. Hopefully, Tommy makes a speedy recovery, but fingers crossed that I can play my way into the Six Nations."
He was also a member of the Ireland squad that travelled to New Zealand for the 2011 World Cup and started the game against Russia during the tournament – incidentally, he replaced Bowe on the right wing after the Monaghan man suffered an injury in the previous game.
Rather than bemoan not being selected regularly in his favoured position, McFadden credits his versatility and ability to cover a multitude of positions as one of the main reasons behind his selection for the squad.
"I don't think I'm missing out. There's been positives to it, like being selected for the World Cup squad from a place where I didn't have a lot of caps and I covered a lot of positions. That worked in my favour, but I think at this stage, obviously, I am hoping to clamp down one position because it puts you in better stead when it comes to international duty."
Whether that position will, indeed, be in the centre or on the wing is moot at this moment in time. He is getting regular game time with Leinster on the wing and while he did start in the centre for Ireland against Wales in last season's Six Nations – after Keith Earls withdrew for family reasons – it is out wide where he is making most gains.
"I've been mixed and matched and moved in and around. But I just said to Joe, could I get some consistent (rugby), whether it's on the wing or in the centre, for a few weeks in a row because that's when you play your best rugby, when you're playing in the same position.
"I'm getting what I've asked for from Joe. We have a great squad here so it's going to be tough to get into the side, so if I have to adjust then I'm happy to do that. What's important is that I'm playing."
The goal, of course, is to add to his 16 senior internationals caps. He was on the bench for the two Tests in November and played against Fiji, so he's certainly in Declan Kidney's thoughts. A good showing for Leinster over Christmas is what's needed.
"Hopefully, I can put pressure on Deccie to play me somewhere. These games over the Christmas are very important for me, as they are for the team. We need to bounce back from the disappointment of losing to Clermont," he added.