This means he will miss at least tomorrow night's trip to Melbourne and the looming showdown with the Hurricanes.
But that setback, coming on the heels of losing Aaron Cruden for the season, is far from a death knell for coach Dave Rennie's side.
The Chiefs have the second-most points in the competition and a large portion of that haul was accrued without Retallick in their ranks.
An injury to the opposite shoulder during the third game of the campaign put Retallick out for the next four matches and showed his side was perfectly prepared for life without the reigning world player of the year.
Mike Fitzgerald will replace Retallick for the Rebels clash and, presumably, for as long as the All Black takes to recover. The Manawatu lock will link with Matt Symons in the pack, re-forming the combination that enjoyed such success earlier in the year.
Before Retallick returned from his first shoulder injury, Fitzgerald and Symons held the top two spots for game time on the Chiefs. Fitzgerald was then the unlucky man out, while Symons is now No 1 after racking up 730 minutes, increasing his standing within the side.
"Matt's been massive for us," Rennie said. "He really runs our lineout, he was our pre-season captain and he captained us last week, so his experience is good for us. I think he's taken a lot of confidence in what he's done."
The Englishman agreed with that assessment, saying this season had been his best since moving to New Zealand in 2012. But he downplayed his own form.
"It's good getting consistent rugby under your belt," he said. "And the team's going well - that's the main thing. I'm not too fussed about my own form, as long as I'm helping the team to win."
Symons said he had been aided immeasurably by the amount of match practice he had already enjoyed with Fitzgerald, and he was confident Retallick's absence would do nothing to preclude further victories.
"When you lose one of the world's best it's always a big loss," Symons said. "Especially someone like Brodie - he brings a lot to the team and the environment. But me and Mike played a fair bit together this year and we've got a really good working relationship."
Cane, meanwhile, is second in playing minutes among the Chiefs, and his ever-presence makes him eminently qualified to judge the damage done by Retallick's injury.
And while he felt for his teammate, who only recently rediscovered his groove, Cane expected the Chiefs to weather the blow and march on.
"It's a disappointment for him, but throughout this team there's been injuries and guys have just stepped up," he said. "That's the great thing about this side and we expect the same."
