Four players were sin-binned for a brawl as South Sydney Rabbitohs slumped to a second straight NRL defeat, going down at home to Newcastle Knights on Friday.

Tempers frayed as league action returned following State of Origin I, with Tom Burgess involved before his brother and captain Sam joined a melee on the stroke of half-time.

Both men were sent to the sin bin, along with opponents Daniel Saifiti and Lachlan Fitzgibbon, although Newcastle wanted to see Tom Burgess sent off for an alleged headbutt.

"Our boys are just breaking it up, so that's two from them that's got to go," Knights half-back Mitchell Pearce said, according to NRL.com. "One's got to get sent off. If he [Tom Burgess] headbutts him [Saifiti], he's got to go."

The incident marred the Knights' sixth consecutive NRL victory, with their 20-12 triumph a first in 10 against the Rabbitohs, who had also lost to Parramatta Eels last week.

Newcastle scored early through Hymel Hunt and, although James Roberts then went over, the visitors' lead was extended by Mason Lino's penalty and Mitchell Barnett's score.

After the 39th-minute brawl, Dane Gagai - Queensland's hero in the midweek Origin victory over New South Wales - dispatched a penalty going into the break.

The Knights maintained control, though, and Connor Watson crossed before Lino executed another penalty goal, with Sam Burgess' late try counting for little.

In the late game, Canberra Raiders eased to an 28-0 win at Wests Tigers.

The Raiders were dominant throughout and scored through Bailey Simonsson, Jordan Rapana, John Bateman, Jarrod Croker, who also kicked four conversions, and Aidan Sezer.