Last updated on .From the section Welsh Rugby

Derbies between Welsh sides could still be protected if an expanded Pro12 splits into two conferences

Former Wales flanker Martyn Williams believes it would be a mistake to split an expanded Pro12 into two conferences.

South African sides Cheetahs and Southern Kings are set to join the league for the 2017-18 season.

Derbies are likely to be protected even with a split, but Williams says the league should not complicate matters.

"I think you should just go with a league. I know there's extra games to be played, but just play each other home and away," Williams said.

"It'll be so confusing if you've got two conferences, two of seven and working out who plays who.

"We've got to keep all our Welsh derbies, because they're the games that bring the crowds in."

Martyn Williams played his 100th and final Test for Wales in a capped match against the Barbarians in 2012

Former Cardiff Blues open-side Williams, who won 100 Wales caps and played four British and Irish Lions Tests, admits that the Pro12 does have to change to survive.

"Ultimately it's all about money... you're up against two absolute juggernauts of league in the Aviva and Top 14, England and France respectively," the 41-year-old told The Friday Night Social.

"The Pro12 needs to look at other revenue streams because it's not quite working as it is.

"The South Africans... will be stronger than the Italian teams and in fairness the people in charge of the Pro12, it's not a knee-jerk reaction it's something they've gone through and obviously the numbers work.

"If someone is a casual supporter then it will bring a little bit more spice into the league.

"If I was a player I'd definitely be excited about that prospect, something different and another test."