Scarlets and Ospreys, thanks to their strong first half of the RaboDirect PRO12 season look to be well on their way to securing a Heineken Cup berth.
However for the Dragons and the Blues the situation is anything but as secure with the two regions battling it out for the final spot of three.
Heading into the Boxing Day clash it is the Blues that have the upper hand with a seven-point advantage over Sidoli and co.
However with the Dragons having a game in hand over their near rivals Sidoli is confident a Boxing Day victory may yet see them come out on top.
"It is the defining game, a huge clash and derby matches - especially over the Christmas period - are the ones that mean everything to the player involved and to the supporters," he said.
"It's a huge game in front of what will hopefully be a huge crowd.
"We've had a very slow start to the season and they beat us at home earlier in the campaign.
"At the moment it's between us and them for that final spot for Europe so this is a game that if we win, we can close the gap and start to push up the table.
"We were so disappointed to lose to them earlier in the season so we have to do it the hard way and rectify it by going away and going after them.
"It wasn't a good spectacle of a game a few months ago, which was disappointing, so hopefully this Boxing Day fixture can be a great game to watch and be a part of and which will turn the momentum our way.
"Form doesn't seem to count in derby games.
"On the day, it's about that general hunger and whoever is the most hungry will be the team that comes out on top."
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