The All Blacks loose forward, who had taken the Super Rugby season off to concentrate on making the sevens team for Rio, failed to make coach Gordon Tietjens' final selection on Sunday.
The 32-year-old, who won Commonwealth Games gold medals in sevens in 2006 and 2010, had been made aware he had missed out on the final Rio selection prior to the public announcement, Chiefs coach Dave Rennie said.
Rennie told the Waikato Times earlier this week that Messam would be in the matchday 23 for the Reds' clash at Lang Park in Brisbane but was unlikely to start, which was confirmed on Wednesday.
Rennie said the 43-test All Blacks' flanker had been working on adding muscle to his frame after dropping weight to play the shorter version of the game.
"He's made a real emphasis on trying to put on a bit more size. But he looks good," Rennie told the newspaper. "He's in pretty good nick, obviously, and keen to contribute.
"He's always loved playing for this team and he's excited that there's still a bit of footy for him to go back to."
Messam also missed out on the 2011 World Cup squad at the last minute, only to battle back and become the All Blacks' first choice blindside flanker until 2014 when Jerome Kaino returned to New Zealand from Japan.
He made the All Blacks' 2015 World Cup squad then went to play for Toshiba in Japan. He will return to the club later this year before playing for the Chiefs again in 2017.
All Blacks openside flanker Sam Cane will shift to number eight against the Reds, while lock Brodie Retallick has been given the week off.
New Zealand scrumhalf Tawera Kerr-Barlow and flyhalf Aaron Cruden, who came off the bench in the Chiefs' 23-13 victory over the Canterbury Crusaders in Fiji last Friday, have returned to the starting lineup.
Centre Charlie Ngatai, who was named in the All Blacks squad for the test series against Wales last month but did not play due to lingering concussion symptoms, was not considered.
"He's still got really mild symptoms, and until he comes right he can't start training," Rennie said.
"So unless he comes right in the next couple of weeks the chance of him playing for us again this season is pretty slim."
(Reporting by Greg Stutchbury; Editing by John O'Brien)
