The New Zealand Herald understands Retallick, who has been sidelined by a shoulder injury, is on track to return for the All Blacks' match against Namibia on October 6.
The 28-year-old was due to remain on the sidelines until the quarter-final stages of the tournament, but his recovery was progressing faster than expected.
It was confirmed yesterday that Retallick would miss the All Blacks' opener against South Africa on Saturday night, putting to rest the suspicions of Springboks forwards coach Matt Proudfoot, who was prepared for Retallick to be named in the game-day squad.
"Steve Hansen said they had a full squad to pick from, that was his last press release so I wouldn't be surprised if they have a little trick up their sleeve," Proudfoot said at a press conference earlier in the week.
While coach Steve Hansen decided Retallick wasn't ready to return for the opening game, he did note Retallick looked good in training. When asked at a press conference if Retallick would return during pool play, Hansen said: "we'll have to wait and see."
Retallick's return would be a big boost for the All Blacks, with former captain Sean Fitzpatrick having said this week that another locking injury would put the hosts in "big trouble".
"Having lost Retallick for at least the early pool games, if we lose Sam Whitelock or Patrick Tuipulotu then we are in big trouble. The All Blacks squad is still good enough to beat most teams and it is just a question of can we do it over three major games which is a huge workload and you have to be able to rotate players."
Though they appear set to get Retallick back for an extra two games, the All Blacks are taking precautions with loose forward Matt Todd, who suffered a shoulder injury in training.
Hansen suggested Todd's injury wasn't serious, but at this early stage of the tournament the All Blacks were unwilling to risk their players.
Loose forward Luke Jacobson has already been ruled out of the tournament due to concussion and was replaced in the squad by Tasman's Shannon Frizell. With the injury to Todd, Frizell has found himself inserted straight into the matchday squad with a spot on the bench against the Springboks.