Former All Black midfielder Fekitoa, in his first season at the English club, has credited the 21-year-old first-five for transforming Wasps' attack in the absence of of another ex-Kiwi international, Lima Sopoaga, due to illness.
Sopoaga is now back in contention for selection but has struggled to make an impact since signing with Wasps in 2017 and Umaga's impressive form will only have put more pressure on the 18-test All Black.
"He's been playing really well and is already leading us forward. You can see he can handle pressure and do amazing stuff as well – for one so young he's going to be great for the club," Fekitoa told The Rugby Paper.
"It's exciting because he can break a tackle and is fast as well. His game-management is growing and you can see our attack has been getting better. At the same time, Lima is back now after his illness and we have Billy Searle, so it's great to have that competition between them."
Umaga had a brief stint in New Zealand in 2018 as he helped Auckland win the national provincial title.
His father, former Samoa international Mike Umaga, was also born here before moving to England in the mid-1990s.
It was in the UK where Jacob was born and having already represented England at under-20 level, it would appear that is where his future lies.
Fekitoa has no doubt his strong family history in the game will hold him in good stead.
"I never played against Tana but he was a great player for New Zealand who everyone looked up to and you can see that runs through the family," he told The Rugby Paper.
"Jacob has spoken to Tana many times and learned a lot from the guy, so hopefully he can continue bringing that leadership to us."
Meanwhile, Fekitoa gave a ringing endorsement to Ian Foster as he prepares for his first season in charge of the All Blacks.
Foster was a polarising appointment but Fekitoa, who played 24 tests for the All Blacks between 2014-17, is confident he's the right man to take over from Steve Hansen.
"I was really close to him and not only did he develop me as a player on the field, off the field he understands players very well and makes sure everything is okay," Fekitoa said.
"If everything's sorted off the field, you tend to play better and I'm sure all the younger guys coming through will like and respect him. The All Blacks are in good hands."