The Roosters will sweat on scans of key forward Sio Siua Taukeiaho, who suffered a pre-game knee injury before an "unacceptable" defensive effort from their middle men against the Rabbitohs.
South Sydney's big men ran riot in a 26-14 triumph over their arch-rivals, with their starting pack clocking 22 tackle busts and plenty of metres through the middle as Tom Burgess, Damien Cook and Junior Tatola all made clean busts early in the game.
Sio Siua Taukeiaho's last-minute scratching came from a contact injury suffered in the Roosters warm-up, though club doctor Ameer Ibrahim confirmed the Tongan international had not suffered a second ACL rupture as first reported elsewhere.
The 26-year-old will require further assessment over the weekend after initial scans on his knee proved inconclusive.Losing Taukeiaho appeared to rattle the Roosters middle, with replacement prop Dylan Napa and senior man Jared Waerea-Hargreaves missing five tackles each in an underwhelming start.
Bench prop Zane Tetevano expects an uncomfortable review session when the Roosters regroup ahead of their clash with Canterbury Thursday week.
Match: Roosters v Rabbitohs
Round 6 -
Venue: Allianz Stadium, Sydney
"That wasn't up to our standards, it was unacceptable for us," Tetevano told NRL.com.
"They played well, but those misses in the middle, that's not us. It's back to training for us on Saturday to get things right.
"We gave them a sniff at the start and that got them going. They put on a display, but you've got to shut them down early in a game or they do get excited and get going like that."
Coach Trent Robinson took heart from his team holding Souths to 8-8 despite barely getting a look-in over the first 30 minutes.
Two second-half errors under the high ball from James Tedesco proved the game's turning point, but Robinson lauded his fullback's effort in trying to pull the result back.
"That start of the second half was disappointing," Robinson said.
"That was disappointing there for Teddy but then when it came to his ability to play after that he was the one that kept probing.
"That was a real positive there about his involvements and attacking the ruck, I thought that was good."
Roosters press conference - Round 6