England head coach Eddie Jones says rugby union may need two referees on the field to keep up with the increasing intensity of the game.
Jones was speaking following England's 12-11 win over South Africa, in which referee Angus Gardner decided against penalising captain Owen Farrell for a last-minute tackle on Andre Esterhuizen.
Gardner went to the TMO but chose not to award South Africa a penalty, which would have given the Springboks a chance to steal the win from the tee.
Farrell has since escaped punishment for the tackle after World Rugby decided not to cite the England fly-half, but Jones says the fallout over the decision shows how difficult a job referees have and that an extra official on the pitch would help.
"I just think the game is getting more intense. All the data shows that," Jones said.
"The game [against South Africa] went for 100 minutes on the weekend with 39 minutes of ball in play. So there was 61 minutes where the players could recover, adding to the intensity of the hits, the quickness of the contact.
"We are asking one referee to do it the way they did it when blokes like me were playing -- jogging around the field basically. And he's still doing the same job.
"So I think the referees are doing a great job. At some stage in the future, probably not in my time, they may have to look at two referees on the field. They do it in rugby league in Australia."
Elsewhere, South Africa have made light of their controversial defeat to England after a video emerged from their training camp showing Esterhuizen imitating Farrell's tackle, under the guidance of head coach Rassie Erasmus.