NRL General Manager – Officiating Tony Archer has detailed the reasons behind the decision to deny Ben Barba a try in the Sharks' victory over the Knights on Sunday afternoon.

Cronulla hooker Michael Ennis was penalised for obstructing Knights opposite Chris Adams, and while the play was initially sent to the bunker as a try, Archer explained it was the right call for the review officials to overturn the on-field ruling.

"It's an unusual one, but you can see Michael Ennis comes out from dummy-half, passes the ball," Archer said.

"He's in front of the ball-carrier and he continues to move forward and impedes Adams, the Knights defender, who's trying to come across and tackle the ball-carrier.

"At that point that constitutes an obstruction, and the bunker correctly overturned a live decision and ruled no try. 

"That's a penalty to Newcastle."

Barba would go on to score two tries in the contest as the Sharks recorded their 15th consecutive win.

Also in this week's NRL HQ, Archer provided insight into the decision to deny tries to Warriors flyer David Fusitu'a and Dragons centre Taane Milne, and discussed penalty counts in Round 20.

Watch NRL HQ