Samoa may have got their World Cup campaign back on track with a rousing win over Greece, but they didn't emerge unscathed after an injury to a key squad member was revealed in the aftermath.

Manly Sea Eagles forward Josh Aloiai suffered a suspected dislocated kneecap during the contest, with scans expected to reveal the extent of the injury in the near future.

The injury occurred midway through the first half, and coach Matt Parish confirmed afterward that it wasn't looking great for the back-rower.

“He's not great. Early signs (show it) may be a dislocated kneecap,” Parish said after the game.

“He's in a bit of pain and a leg brace, it doesn't look promising at the moment.”

If Parish's worst fears are confirmed, it will likely rule Aloiai out for the tournament with a recovery period in the area of six weeks.

The heated clash between Lebanon and Ireland also resulted in injury, with Cedars forward Kayne Kalache hospitalised after connecting with the shoulder of Gold Coast and Wolfhounds enforcer Jaimin Jolliffe.

Surprisingly, Jolliffe was allowed the remain on the field, and Lebanon coach Michael Chieka couldn't help but seethe at the glaring double standard after Adam Doueihi's controversial send-off in the team's opening clash with New Zealand.

“Kayne wasn't flash if I'm honest,” Chieka said.

“I wasn't happy with the whole thing. We had a player sent-off for supposedly saying something to the referee.

“(But a) bloke takes a shoulder fair and square to the head and nothing happens. Our player goes to hospital. Go figure.”

Meanwhile the competition's strict concussion rules have dealt a blow to the host nation's prospects, with star centre Kallum Watkins now facing an 11-day sideline stint after failing a HIA in the second half of England's Round 2 clash with France.

Watkins had to be helped from the field in visible discomfort early in the second half after being injured in a tackle.