Red-carded players can be replaced 20 minutes after their dismissal in New Zealand's new Super Rugby tournament.
The country's five Super Rugby teams will play a domestic mini-series from 13 June after getting approval to restart the sport behind closed doors.
"Paying rugby fans, players and coaches want to see a fair contest," said New Zealand Rugby's head of professional rugby Chris Lendrum.
"Replacing a player after 20 minutes strikes the right balance."
If teams are level at full-time, 10 minutes of 'golden point' extra time will follow with the first score decisive.
New Zealand Rugby has also tightened rules around the breakdown, requiring both ball-carriers to play the ball and tacklers to roll away quicker.
Teams playing in the mini-series will use chartered planes to travel on match days and players will be checked daily for coronavirus symptoms.
Last week, World Rugby introduced a series of optional adaptations to laws designed to reduce the threat of coronavirus transmission in the sport.