NRL referees boss Tony Archer has claimed Lewis Brown's four-pointer "could have potentially been an eight-point try" after the Panthers second-rower crossed late in his side's narrow loss to the Rabbitohs at ANZ Stadium on Sunday afternoon.

With Aaron Gray sliding across in defence and leading with his knees, Archer said that procedurally, the on-field referees should have sent the try and ensuing contact up to the video referees to be reviewed.

"The situation was Jared Maxwell on-field gave a try live, they went back and in the circumstances of taking a conversion, there were some replays which came up that the video referees saw," Archer explained.

"The conversion was taken before the last replay came into view, the video referee couldn't stop play at that stage, but initially they should've stopped play, checked it, because he led with the knees and made contact with the head.

"That was a potential eight-point try."

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An earlier incident, also involving Gray, saw Penrith fullback Will Smith held back by the Souths winger following a break by Bryce Cartwright.

However in this situation, Archer believes the on-field officials made the correct decision, and didn't think it was necessary for Gray to be sent to the sin bin.

"I think a penalty is an appropriate sanction for that incident, it was a long way away from the play, play continued, they went back and got a penalty and I think that's the right decision," Archer confirmed.

Archer also commented on incidents from the Roosters v Bulldogs clash at Allianz Stadium and the Dragons v Knights game at Jubilee Oval.

For more on refereeing decisions from Round 21, view Archer's full interview here.