Australian Kangaroos forward Reuben Cotter has suffered a concussion that will rule him out of the second match at the Rugby League World Cup against Scotland next week.

Under tournament rules, players will automatically face an 11-day period on the sideline after suffering a concussion as they work through protocols.

The rules are what is used in the English Super League, and are far more stringent than those applied to the NRL, where players can pass through the protocols for a return to play in just six days.

Cotter found himself knocked out during the second half of the 42 points to 8 win over Fiji after a sickening head clash with Tui Kamikamica.

The Melbourne forward also left the field for a head injury assessment, becoming the second Fijian to do so in the game, although Viliame Kikau was able to return.

No news has been provided on Kamikamica's status with regards to the test ahead of what will be a must-win game against Italy next week for the Bati following the loss to the green and gold.

Cotter was the second Australian to be sent for a HIA during the game as well following Murray Taulagi, however, the winger was able to return after the halftime interval.

The Kangaroos will have four players to bring back into the 17 for the game against Scotland next week, with Nathan Cleary, Isaah Yeo and Liam Martin from the Penrith Panthers, and Reagan Campbell-Gillard all rested after playing in the grand final a fortnight ago and linking up with the NRL squad late.

It means one of the forwards will almost certainly replace Cotter, while the make up of the Kangaroos' other changes - of which there could be seven to ensure all of the 24-man squad plays one of the first two games - is yet to be known.

Australia play Scotland on Saturday morning (AEDT), with the team list due to be named by Wednesday night at 9pm (AEDT).