An injury ravaged Newcastle were forced to use three fullbacks in the opening 40 minutes as they blew a first-half lead to lose 30-8 to Penrith on Saturday.

First-choice fullback Darius Boyd lasted just 15 minutes before succumbing to a hamstring strain that happened in the first 10 minutes. Skipper Kurt Gidley then moved from hooker to the back, but he left the field in the final moments of the half with a head knock.

The Knights were restricted to just one fresh reserve for the final 15 minutes of the game when halfback Tyrone Roberts was assisted from the field after a head clash. Newcastle now face an uphill battle, with the important trio potentially joining five-eighth Jarrod Mullen on the sidelines ahead of their round-two match against Canberra next Sunday.

Knights coach Wayne Bennett said Boyd had a tear in his hamstring.

“It wasn’t what we want to happen, but it happened,” Bennett said. “There were a whole lot of situations there that I couldn’t plan for.

“You’ve got guys out of position; that cost us two tries. It’s not their fault, but they aren’t used to playing there. I was elated with their effort. We can fix the things that happened today. They didn’t deserve to get beat by 30-odd points.”

As the Knights suffered, the Panthers pounced.

With Gidley and Boyd off the field, Dane Gagai shifted to the back for Newcastle, and the Panthers took advantage of the restructured defence. Back-rower Alex McKinnon moved to Gagai’s right-centre position as Penrith began to attack.

Down 8-6 at half-time, the Panthers snatched the lead when winger Josh Mansour scored twice inside the opening 10 minutes of the second half. A wide shift to where Gagai would normally be defending caught the Knights short and allowed Mansour to race 30 metres and beat four defenders to give his side the lead for the first time.

Jamie Soward’s boot produced the Panthers' first try of the season to fellow new recruit Elijah Taylor, and the Penrith five-eighth created another opportunity when he secured the first 40-20 of the year. The new tap rule (instead of a scrum) left both teams confused. But the Panthers wasted little time to again target Newcastle’s right-hand side with Mansour getting on the outside of opposite Akuila Uate to score. Co-captain Peter Wallace extended the lead to 10.

Beau Scott shifted to the centres following Mansour’s second try as the Knights attempted to stop the Panthers' onslaught. But even then more points would come for the Panthers on their left edge.

A wide shift when camped inside their own half – instigated by Brent Kite – surprised the Knights defence, as the home side found room again on the flanks. This time it was centre Dean Whare who found space, and he chipped ahead as the Knights' defence scrambled. An unkind bounce deceived Gagai, Whare regathered and he found Adam Docker, who collided with Roberts as he scored.

Both men were dazed and forced from the field. Docker returned for the dying stages after passing the concussion assessment test.

Eventually Jeremy Smith partnered Scott, Uate and Michael Dobson  on the right, but the Knights never recovered from a poor opening start to the second half.

Wallace did the damage with the boot next. He found space to gift interchange prop Jeremy Latimore his first try since 2010.

Soward came from the field late in the second half after struggling with back spasms. Penrith coach Ivan Cleary said he didn’t expected Soward to return after half-time.

“I wasn’t too disappointed with the first half,” Cleary said. “The start of the game wasn’t really like round one. Both teams were pretty accurate. It took a lot out of everyone. Our attack was a bit clumsy in the first half, the boys were out on their feet.

“In the second half the points just came, rather than good execution.”

Both teams struggled in the first half in front of 11,369 fans at Sportingbet Stadium as the temperature soared to almost 30C.

The Knights finished their first 40 minutes of the season with a 55 per cent completion rate. While the Panthers controlled the ball a little better, completing 63 per cent.

After a stagnate first half, Newcastle scored the opening try of the game when a well-timed pass from Dobson found a charging Scott, who broke the deadlock after 32 minutes.