Canberra's star man sensed his moment early in the second half and scored an opportunistic try that wrested complete control of the match from Cronulla.

Andrew Fifita infringed, holding Wighton down in a tackle about 18m out from the Sharks' goal line. Referee Grant Atkins first waved six again, and then blew a penalty.

Instead of dishing the ball to Jarrod Croker to kick a penalty goal, Wighton took a quick tap and caught the Sharks napping to score next to the posts. Captain Wade Graham screamed 'Challenge' at the referee, but was told that was not an option for ruck or marker indiscretions.

"A ruck infringement decision cannot be challenged as it is a discretionary decision under the rules," NRL head of football Graham Annesley said of the incident.

"A quick tap is permitted from a penalty awarded more than 10 metres from the goal line."

A tokenistic visit to the Bunker verified Wighton's textbook grounding of the ball, and Croker's subsequent shot at goal sent Canberra into a two-point lead.

Just minutes later Wighton extended that lead with an acrobatic effort to score from a George Williams cross field kick. Wighton leaped from the ground with no regard for his safety and managed to control the football despite an awkward landing, before grounding the football.

He still wasn't done. Just seven minutes later Wighton charged at a quivering Sharks defensive line before popping an inch perfect pass for his halfback, George Williams. The Englishman muscled between Aaron Woods and Siosifa Talakai for his second try of the match.

In their first season together, Wighton and Williams have grown into one of the game's most lethal halves combinations.

Were it not for Williams' first try, Wighton may not have had the chance to wrest control of this one from the Sharks.

With his side down eight points minutes from the break, Williams came up with a play to keep the Green Machine in touch, picking off a Wade Graham pass and sprinting 65m to outrun Scott Sorensen and score in the corner. It slashed the margin to just four points at the break after Cronulla had dominated the first half.

Back rower John Bateman was lucky to remain on the field just five minutes in after he fouled Braden Uele while the Sharks man chased a Chad Townsend chip kick. Bateman stepped across to initiate contact on the chaser, and was penalised but was not sent for 10 minutes in the sin bin.

As it happened, Townsend appeared to score a try after out sprinting the flailing Raiders defenders but he fumbled the ball at the crucial moment. Cronulla took two points, while Bateman and Canberra dodged an early bullet.

Sharks hooker Blayke Brayley reacted fastest when Elliott Whitehead spilled the ball just five metres out from his own goal line. He scored the try, but didn't get up, clutching his right ankle which buckled awkwardly underneath him as he stretched out to score the try. He limped from the field just minutes later with a suspected syndesmosis injury.

Scott Sorensen was drafted in to replace him, but lasted just 16 minutes after suffering a hamstring and groin injury in the second half.

"We lost young Blayke Brayley our starting hooker who was going real well for us in the first half and then the back up hooker comes on, Scott Sorensen, we lose him as well," Sharks coach John Morris said.

"Andrew Fifita off with a HIA not that far from that period so we were under the pump a little bit. That's when you get tested, big games and big moments.

"That was one of those moments that we had to just make sure it didn't lead to too many points. They pulled our pants down there, three quick tries."