Isaako, who was named the Dally M NRL Rookie of the Year, will make his second test appearance after his debut against England in Denver.
Isaako missed the first test in England for the birth of his first child. He rejoined the Kiwis at the end of last week and will add much needed pace to their back line.
The selection for the third test was unusual.
Initially, the NZRL confirmed a 20-man extended squad— without nominating any positions — but a few hours later Maguire had settled on his 17, with Gerard Beale, Fisher-Harris and Jahrome Hughes missing out, while Taupau was omitted all together.
But Papali'i is the story. The 20-year-old, who captained the Junior Kiwis last month, continues his upward trajectory.
"The future of where you are going is strong when you have young players like that coming in," said Maguire.
"Young Isaiah, he's been perfect on tour. He's done all the training, he's a very diligent young man. So I am looking forward to seeing him have one of many games moving forward but obviously he understands it's a big day and he is after a big performance."
Papali'i was a shock selection for Stephen Kearney's first Warriors game in 2017. After that match against Newcastle, he wasn't sighted again until the end of last season, where he made a further four performances.
But after a strong pre-season under new trainer Alex Corvo, he didn't look back.
He was ever-present from the end of April onwards, and his form was so strong he forced Simon Mannering into a bench role. His defensive workload was outstanding, while his attacking prowess, and ability to find space and offloads where none seemed possible was particularly impressive.
While he had a league background, Papali'i made his name in 1st XV rugby, and was named the best school boy player in the country in 2016 after leading Mount Albert Grammar School to the national title. But he was always going to focus on league after school, and thankfully for the Kiwis he has.
Although he has yet to play a test, already there are comparisons with Mannering and Stephen Kearney, in terms of his precociousness, capacity for training and attitude towards preparation.
He's certainly mature beyond his years, and will need to be against a confident England team, looking to put the seal on a perfect series in front of an expected 35,000 crowd in Leeds.
"[We have] a stronger understanding of what we need to do on the field," said Maguire.
"We are well aware of what England are throwing at us now and it's about doing that on every single play. The concentration around that has been a big part of this training week and the boys are focused on a strong performance."
Kiwis: Dallin Watene-Zelezniak (c), Ken Maumalo, Esan Marsters, Joseph Manu, Jamayne Isaako, Shaun Johnson, Kodi Nikorima, Jesse Bromwich, Brandon Smith, Jared Waerea-Hargreaves, Kevin Proctor, Isaac Liu, Adam Blair. Interchange (from): Kenny Bromwich, Leeson Ah Mau, Isaiah Papali'i, Joseph Tapine.
