Sydney Roosters coach Trent Robinson has refused to pin their season-opening upset to Penrith on a depleted line-up, saying his team simply needed to do better.

The Roosters’ premiership defence got off to a losing start on Saturday after they were overrun by the Panthers by six at Panthers Stadium.

Robinson, who entered the match without rested co-captain Boyd Cordner, also lost star Angus Crichton prior to the game due to a chest infection.

Club doctors were quick to clear him of the coronavirus.

“The doctors were very good in saying they didn’t think it was, but they just needed to get the test back and make sure it wasn’t, and it wasn’t,” Robinson said.

The Roosters got off to a blistering start away from home, racing out to a 12-0 lead before allowing Penrith back into the contest in the final hour.

Robinson also had to contend with crucial injuries to Matt Ikuvalu (concussion) and second-rower Sitili Tupouniua (knee) in the second half.

Robinson said Tupouniua suffered a medial ligament issue, which could sideline the promising forward for a handful of weeks.

Robinson refused to use the constant reshuffling, which included Brett Morris being shifted from right wing to left centre and back to right wing, as an excuse.

“But that’s footy at the moment. Matt was our best player on the field until he went off, and then (we) had to reshuffle again,” Robinson said.

“Lindsay (Collins) ended up playing that whole second half, but we had our starting guys back on there and Sam (Verrills) not long after that.

“So there was no excuses on the changes. We needed to do better for longer.”

Robinson was also unhappy with his team’s last-play options.

In what was their first NRL outing since the retirement of Cooper Cronk, the Roosters’ new halves combination struggled to impose their will on the contest.

“You need to finish your sets well and we didn’t have one good end of set in the first half,” Robinson said.

“I didn’t think we were attacking great for the most part of the game.

“We had kicks back across where they made half-breaks off, we had Jake Friend kick it on last, James Tedesco kick it on last.

“We had a 20-metre restart which they scored off. You turn a bad set into a good set, we turned some average sets into really poor sets.

“There wasn’t one good end of set and that eventually costs you.”