It's for that reason that the Warriors are relaxed about the future of Vatuvei - if he decides on an early release from his contract - because they have a replacement.
Maumalo is averaging almost 150 running metres each game, which is the second highest at the club and among the top 20 in the NRL.
He's a crucial element of the Warriors go-forward, providing strong momentum at the start of every set.
Maumalo has also gradually eased the mistakes and insecurities out of his game, tightening up his defence and becoming safer under the high ball.
It's a stark contrast to his difficult debut year in 2015.
"Back then I was lacking confidence," said Maumalo. "Every week I am still trying to improve, but now I am running onto the field with a lot of confidence.
My ball security, my concentration during training and in the game, all those little things that people may not notice but I have really put a big emphasis on this year."
Maumalo's improvement is the product of a change in attitude
"My preparation has been a lot better - that's the most important thing," said Maumalo. "I'm trying to do all the little things right, like extras after training, which I normally never did."
"In my first year I never focused on all the little aspects. I was just content to play one game when I debuted and happy to be around the boys. Now I see it as a professional sport - it is a job and everything does add up when it comes to performances."
He can be regularly spotted staying behind after team training, catching a ton of bombs hoisted by the assistant coaches, working on his support play or practising his dummy half pass ("there were some wobbly ones in the past")
Like many of the young brigade at the club, Maumalo has also made some necessary tweaks to his diet.
"I used to like having pizzas and junk food, but now I am just having it once a week after the game," said Maumalo. "One cheat meal and then straight back on my diet the following Monday."
Despite the strong start to his campaign, Maumalo remains humble and grounded, and also deeply respectful of Vatuvei.
He doesn't feel he owns the No 5 jersey, even though it is increasingly the case.
"I still feel for him - he is going through a tough period," said Maumalo. "Every time I put on that five jersey I put it on with respect.
I know it is not my jersey but it is all the people that have come before me. It's up to me to perform in that jersey and I know Manu will come back strong."
