It emerged last night that 45-test veteran Sitiveni Sivivatu could also find himself on the outer.
The New Zealand Herald understands Waikato loose forward Messam and Wellington winger Gear will be joined by prop Wyatt Crockett and lock Jarrad Hoeata as players who were with the All Blacks in South Africa but have not made the 30-man cut.
Hoeata looks likely to miss out after North Harbour lock Anthony Boric's just-in-time recovery from a foot injury suffered in June.
Messam appears to have been overtaken by Wellington's Victor Vito as cover for No 8.
Last night, Messam, Hoeata and loose forward Jerome Kaino arrived at Auckland Airport after the All Blacks' weekend loss to South Africa.
Kaino has been given leave from the squad before the Tri-Nations decider in Brisbane as his partner is due to give birth.
Messam and Hoeata declined to comment on their World Cup fortunes.
Gear and Sivivatu shape as the unlucky ones in the jostle for the back-three positions.
They are likely to miss out to certainties Mils Muliaina and Israel Dagg, and Cory Jane, Isaia Toeava and Zac Guildford.
It is thought the selectors have a 1st XV in mind and favour players who can play in more than one position to cover the fullback and wings.
Gear and Sivivatu, specialist wings, have slipped down the pecking order against more versatile players.
It will be a particularly cruel cut for the Gear family. Four years ago, Rico Gear, who had played 19 tests, was considered one of the unluckiest players to miss Graham Henry's squad for the World Cup in France.
Hosea Gear has played only eight tests, but his form on the end-of-season tour in November was so strong he appeared to have pushed himself to the front of the World Cup queue. Indifferent displays for the Hurricanes and All Blacks this year have hurt.
