European rugby chiefs cancelled a total of five fixtures – four in the Champions Cup – but with the World Cup further compressing an already cramped calendar, finding free dates to accommodate the unplayed fixtures will prove difficult.

Possibilities include scheduling a midweek fixture or putting back domestic fixtures to create a window for the games, but English side Bath, who face Leinster this weekend, have insisted that neither is a workable option for them, claiming their Pool 5 tie against Toulon is now unlikely ever to be fulfilled.

While the Pro12 and Top 14 began their leagues before the start of the World Cup, England’s Aviva Premiership delayed their kick-off until mid-October, making finding a free date even more difficult.

Bath chairman Bruce Craig told The Telegraph: “It is very clear to me that the Toulon match can’t happen.

“The midweek option is not an option to my mind as that would to the detriment of player welfare as well as the integrity of two competitions, an important Champions Cup game being squeezed in with all the attendant travel issues between two Premiership weekends.

“There is no way we should be letting that happen. You can’t play three high-profile games in a week.

“In the wider context of what has happened in Paris, this is not a serious matter, of course it isn’t. And I do understand why the decision was taken.

“But from a rugby point of view, and from the point of view of the competition, this is an issue of significant consequence. There is no place to fit it in. It is a bit of a disaster in that regard.”

Ulster and Oyonnax do share a free weekend at the beginning of February, a fortnight after the French side’s visit to Belfast in what would otherwise be the final weekend of the pool stage, but that would clash with the first set of Six Nations matches.

Ulster manager Bryn Cunningham has conceded the difficulties posed by the congested fixture list, but insisted the province would be ready to deal with whatever issues are thrown up by European rugby’s decision regarding the Oyonnax game.

“Already our management team is planning the weeks and months ahead to see what our fixture list looks like and any potential impact this will have,” he said.

“Other clubs will be doing the same and we just have to manage that and have the squad prepared for a midweek game or for a game to be shifted to later in the season.”

Should any game fail to be rescheduled, competition bosses may even have to resort to a little-known mathematical system used to decide the results of abandoned amateur matches in France, known as periequation-equalisation, which is similar to cricket’s Duckworth-Lewis method.

EPCR say they will consider all the options available before deciding what to do, with its chairman, Simon Halliday, saying: “This is going to be a consultative process with all those involved, and will not be a matter of us quoting the rule book and telling people to get on with it.

“It is an unprecedented situation and it is important we take into account all sensibilities.

“We will make the right decision for all concerned.”