Toopi, one of the best centres of his generation, told AAP Halasima was his favourite player in the NRL today.
Lauiti'iti, a second-rower like Halasima, incredibly played more than 400 NRL and Super League games, with 115 for the Warriors.
Toopi said Lauiti'iti was "without doubt the best forward I played with", but added that Halasima had the world at his feet.
Ahead of the home clash with the Titans on Saturday Halasima has already scored 17 tries in 35 games and made 10 line breaks, the kind of record a star back would be proud of.
"No doubt Leka will be in the history books at the end of his career, but we are only seeing him scratch the surface," Toopi said.
"Over time he is going to be one of the greats, but he is still a young pup and hasn't yet fully understood what his capability is.
"He is still establishing himself as an 80-minute player at the highest level, but we have another year or two before we truly see his maturity and game awareness to pick his moments."
It is Halasima's unpredictability about when he carries the ball, all muscle and athleticism, that makes him stand out.
"You look at him and you think athlete, fit, fast, strong," Toopi said.
"Sometimes when you have to carry the ball out of your own half as a forward it's a predictable 'truck it up and get a quick play-the-ball'.
"For him I feel like there are so many strings to his bow. He offers a lot more than your traditional 'up and down' back-rower."
The 188cm Lauiti'iti terrorised opponents with a skill set that had to be seen to be believed.
Halasima and Lauiti'iti both share game-breaking qualities, but Toopi said his former teammate was "out of the game box".
"I don't think you can ever replace Ali," he said.
"Ali could offload, fend you off, step you and run around you while holding the ball in one hand.
"Leka is showing us glimpses, but Ali was doing it regularly. He is still a long way from what Ali did, but there will come a time."
The Warriors, fresh from thrashing Melbourne, have done a great job developing Halasima, and the Tongan international is a huge reason why they sit inside the top four.
"It is exciting times for the club and Warriors supporters to see an absolute weapon and home-grown talent," Toopi said.
"I just hope he gets to stay at home but doesn't get too comfortable as he understands professionalism and not resting on the talent he has naturally got."