The injury suffered to Retallick's left shoulder is the opposite joint from the ailment that saw him miss six weeks earlier in the season.
It's a blow for the Chiefs, coming in the same month Aaron Cruden was ruled out for the season with a knee injury, though Retallick will at least be able to return for the run in.
The lock will miss Saturday night's trip to Melbourne, after which the Chiefs have a bye before a top-of-the-table clash with the Hurricanes in Wellington.
He will be replaced against the Rebels by Michael Fitzgerald, linking with Matt Symons to reform the same locking combination that accounted for Retallick's earlier absence.
Chiefs coach Dave Rennie has made a number of other changes to his run-on XV, with Andrew Horrell getting a chance in the No10 jersey. Marty McKenzie started at first five in the Chiefs' first match without Cruden, but the versatile Horrell now has an opportunity.
Liam Messam returns to blindside flanker after a week's rest, James Lowe has overcome injury to take his place on the left wing, and Pauliasi Manu and Ben Tameifuna will take over in the front row.
Chiefs team to play the Rebels in Melbourne on Saturday night:
1. Pauliasi Manu, 2. Hika Elliot, 3. Ben Tameifuna, 4. Matt Symons, 5. Michael Fitzgerald, 6. Liam Messam (c), 7. Sam Cane, 8. Michael Leitch,9. Brad Weber, 10. Andrew Horrell, 11. James Lowe, 12. Sonny Bill Williams, 13. Charlie Ngatai, 14. Tim Nanai-Williams, 15. Tom Marshall. Reserves: 16. Quentin MacDonald, 17. Siate Tokolahi, 18. Jamie Mackintosh, 19. Michael Allardice, 20. Johan Bardoul, 21. Augustine Pulu, 22. Damian McKenzie, 23. Bryce Heem.
