The former New Zealand mentor has been appointed Samoa's sixth permanent coach in as many years but doesn't officially take charge until January.
He was listed as a "technical advisor" during the team's runner-up finish at last month's Oceania 7s and is with the team in Dubai this week as an "observer".
Assistant coach Stephen Betham, who led the Manu to the 2010 World Series title, said Tietjens had been heavily involved with their preparation.
