The number of guaranteed Welsh derbies in the Guinness PRO12 for each Welsh Region is set to be cut from six to four as part of the radical competition overhaul due to be announced in the coming week.
PRO12 bosses are expected to announce a two conference system which will see seven teams in each with the addition of South African sides the Cheetahs and the Kings. It will effectively then become the PRO14.
But as each conference cannot have more than two teams from the same country, the Welsh Regions are to be separated down the middle, with the Scarlets and Blues in Conference A and the Ospreys and Dragons in Conference B.
Teams in the same conference will play each other home and away, but games against those in the other conference will only be on a one-off basis.
It means the overall number of Welsh derbies over the course of the ordinary campaign will reduce by a third, from 12 to eight matches.
The new system is bound to cause controversy among supporters for whom all-Welsh league clashes are the highlights of the campaign, particularly around the Christmas and New Year period with bumper crowds flocking through the turnstiles.
It also throws into doubt the future of the Judgement Day event which sees an annual double-header at the Principality Stadium and which has grown in popularity over recent seasons.
The Regions will be unhappy to lose two derby encounters and could now be reluctant to cede home advantage by moving games to the Cardiff arena.
However with speculation that TV and sponsorship money, once the South African teams come on board, being worth £10m, any loss of revenue because of fewer derbies looks set to be more than offset.
With the PRO12 hierarchy set to finalise plans for next season at meeting on Tuesday, details are emerging of how teams will be split.
It will be based on the standings of the final table last season after 22 matches.
Working down alternately from top to bottom of the standings from last May sees Munster, Scarlets, Ulster, Blues, Edinburgh, Zebre and either the Cheethas or Kings in Conference A.
In Conference B it will be Leinster, Ospreys, Glasgow, Connacht, Treviso, Dragons and again, either the Cheetahs or the Kings.
Play-offs will continue to determine the winner once the final 21-match tables are known.
Presumably, the winner of Conference A will play the runner-up in Conference B at home, and vice versa.
