A late Dylan Walker double has ended the Sydney Roosters undefeated start to the NRL season, gifting Manly an 18-12 victory.

In a tough and gritty match at a wet Allianz Stadium, Walker broke a 12-12 deadlock in the final two minutes when he burst onto a Brian Kelly ball to run through a yawning gap and 40 metres to score.

Making matters worse for the Roosters, they could lose Queensland Origin contender Dylan Napa for a number of weeks after he succumbed to an ankle injury.

The uncompromising young prop was taken from the field in the 18th minute with a possible ankle syndesmosis and did not return.

Manly, who drifted close to wooden spoon favouritism after starting the season with two straight losses, have now won three consecutive games to sit within the top eight.

They beat an undermanned North Queensland 30-8 in Townsville before dismantling Canterbury 36-0 at Lottoland last weekend but Friday’s win was easily their most credentialed.

The Sea Eagles stole the lead in the 67th minute when Blake Green grubbered for Walker to score his first, breaking a 49-minute deadlock.

However the Roosters hit back with 10 minutes to go, when halfback Mitchell Pearce carried over four Manly forwards next to the posts to level the score at 12-12.

Pearce then missed two opportunities to take the lead with field goals.

His first was charged down by Apisai Korisau and he miscued the next from right in front in the ensuring repeat set.

Cherry-Evans also missed a shot from close range but it mattered not as Walker raced away to score in the final minutes.

His opening four-pointer was the first time the scores changed from 6-6 since the 18th minute.

Shaun Kenny-Dowall grabbed the first try of the night in the 14th minute but the Trbojevic brothers combined for Manly to hit back quickly.

Jake slipped an offload after a powerful burst, then Tom threw a long pass to a wide-running Jorge Taufua.

The Roosters should have gone to the break 8-6 up but Michael Gordon missed a relatively easy kick from the left of the posts after Walker was penalised for back chatting.