NRL General Manager – Officiating Tony Archer has outlined the reasons behind a decision to rule a Wests Tigers goal-line dropout when a second ball appeared on the field during the Knights-Tigers Round 6 clash at Hunter Stadium on Sunday afternoon.

In bizarre circumstances, Knights forward Korbin Sims kicked the second ball away, with Jordan Rankin then contained in his own in-goal.

"It was a very unusual incident," Archer said on NRL HQ.

"The ball was grounded by Wests Tigers after a kick from the Knights.

"For the referee to determine there's a mutual infringement has occurred he has to determine, and he is the sole judge of this, if the play is irregularly affected."

"In circumstances where play has been irregularly affected he would rule a scrum 10 metres out from the goal line and Newcastle would have had the loose and feed."

For more, watch the Round 6 Referee Review