Rees-Zammit made his international return as a replacement in the second half against Argentina to win his 33rd cap.
The 24-year-old came back to rugby with Bristol this summer after two years attempting to make it in American football.
The wing will make his first start since the 2023 World Cup quarter-final defeat to Argentina and attempt to add to his tally of 14 international tries.
“He played a good few minutes last weekend and we feel he’s ready to return to the starting line-up,” said Tandy.
“I think we’ve definitely seen lots of how we want to play against Argentina. There was lots to be pleased about – our attack I thought was excellent and I saw a lot of physicality – but there’s lots to improve.”
Saturday’s Test in Cardiff is crucial prior to December’s World Cup draw with 12th-placed Wales needing to win to stay above Japan in the rankings, and remain in the second pot of seeds for the 2027 tournaments.
Tandy is hunting a first win since taking the reins this summer after Wales ended an 18-Test losing streak with victory in Japan under interim boss, and now attack coach, Matt Sherratt.
Japan are due to name their team for Saturday’s game on Thursday evening.
