Marshall conceded on Wednesday that he had dismissed the Chiefs' threat up until Luai walked into his office this week and told him he would move to the start-up franchise in 2028.
Luai will remain with the Tigers in 2027 after triggering an option in his contract.
But his move to become the Chiefs' foundation signing is likely to attract more players, who may be tempted to earn tax-free money playing out of Port Moresby.
"I don't think anyone was probably that worried about it before - until now," Marshall said on Wednesday.
"It's realistic, if you're chasing more money and a better deal, then there's great opportunities there for you.
"I think every club probably needs to be on their toes for a bit.
"We've got guys coming off contract, but they can't negotiate with them till November.
"For those guys that we've got, it's up to us to try and keep them here before November comes around."
The Chiefs were able to snare Luai because of clauses in his contract and will be free to talk to other players from November 1.
Currently the Tigers have 11 players, including Terrell May, Taylan May, Sunia Turuva and Heamasi Makasini, who can field offers from the Chiefs or rival NRL clubs later this year.
The Tigers and fullback Jahream Bulla are yet to agree to terms on a deal for next year.
"I don't talk about recruitment publicly, but that's what the salary cap is for," Marshall said.
"(You have) to try and fit everyone into a puzzle, this opportunity gives us (the chance) to try and keep all those players that we want to keep."
The Tigers waived the cooling-off period with their star five-eighth, who Marshall hailed as integral to the club's turnaround.
Luai arrived at Concord after winning four straight premierships with Penrith, while the Tigers had picked up three consecutive wooden spoons.
The club finished 13th last season but are on the right track to end a finals drought stretching back to 2011, sitting third with five wins from their first seven games of 2026.
"I've got a guy who I begged to come out of a four-time premiership-winning team to help a club off the bottom of the table progress into a better position," Marshall said.
"He took that challenge with us, and he's 18 months into that deal, and what he's done has only been positive."
Luai is on a salary worth $1.2 million and his exit will give Marshall some time and a fair bit of cash to map out the Tigers' roster for the 2028 season.
"We have been planning for 2028 anyway, so it's a great opportunity for us to have a look at what we've got and make decisions accordingly," Marshall said.
