Loose-head prop Robinson was overlooked for McKenzie's first squad last year before being recalled for the end-of-season tour, playing second fiddle all along to James Slipper.
But Brumbies young gun Scott Sio is more dynamic and has been in better form this season, while tight-heads Ben Alexander and Sekope Kepu can also play No 1.
Even though the Wallabies No 8 jersey is vacant with Ben Mowen France-bound and ineligible for the World Cup, the injury-plagued Palu has been in and out of Super Rugby action.
He remains a threatening line-bender but Western Force's Ben McCalman and Rebels skipper Scott Higginbotham have been two of the best No 8s in the competition and look better fits in a starting back-row to feature Michael Hooper and Scott Fardy.
Mowen's lineout calling and jumping capabilities will be sorely missed and makes Queensland lock Rob Simmons a certain test pick as a prime jumper and caller.
The fact McKenzie needs another works into the hands of NSW captain Dave Dennis, who was also on the fringes of the squad last year when 116kg powerhouse Palu was sidelined.
McKenzie will pick on form but he's also certain to show loyalty to the tour party that enjoyed a 4-1 record in Europe last November.
Centre Kyle Godwin deserves a call-up but he could well be one of five inside centres.
- AAP
