Rainbow Cup organisers are hoping to trial a new 20-minute red card rule for the upcoming tournament, RTÉ Sport understands.

It is among a number of experimental law trials requested by the Guinness Pro14 for the newly formatted competition, which includes the Pro14 teams as well as four South African franchises: the Bulls, the Lions, the Sharks and the Stormers, and runs from 24 April to 19 June

If approved by World Rugby, the law would allow teams to replace a player who receives a red card after 20 minutes with one of the replacements.

The dismissed player would not be allowed to return, but it would mean that the deterrant of a serious foul play would be reduced with teams only reduced to 14 for 20 minutes - double the sanction given for a yellow card.

Two other law trials have been requested, both of which are currently being trialled in Super Rugby Aotearoa in New Zealand.

Organisers want to introduce a 'captain's challenge’, which would allow a team to challenge a call made in relation to try-scoring or foul play, or any decision in the last five minutes of the game.

Footage of the play would be reviewed by the TMO with the referee having the final say.

Teams would be restricted to one challenge, which must be flagged within 10 seconds of the referee’s whistle, and from the last passage of play only.

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A successful challenge would mean the team keeps their option to challenge again, while it would be lost if unsuccessful. 

World Rugby, it is understood, has also received a request to trial goal-line drop-outs in the event of the ball being held up over the line, knock-ons over the line or the ball being grounded by the defence following a kick-through.

The defending team must take a drop-kick from anywhere on their own try-line. In Super Rugby the kick must go past the 5m line. 

This is seen as an effort to speed up the game by reducing the number of scrums required.

World Rugby told RTÉ Sport that they are open to new trials in various competitions and generally approve such requests quickly. 

The Pro14 season comes to an end over the weekend with Leinster hosting Munster in the final at the RDS tomorrow (5pm). 

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