A goal in each half from the youngster - his first senior strikes for the Foxes - saw Enzo Maresca's men past the Millers in South Yorkshire. Fred Onyedinma equalised for the home side early on in the second half but yet another late goal won it for City, who have five successive victories at the start of a new season for the first time in their 139 years of history.
Late goals are becoming a theme and Maresca credited his players for sticking to the game plan, intended to tire their opponents and create space in behind in the final moments. "Since we started, I said with the way we play, because we play a lot, the opponent will run," the Italian said. "In the last minutes of the second half, we'll find more chances, more spaces. It's a journey, a process. It's not easy, but I can see day after day that they are working well and that they understand what I want."
There was just one change to City's XI after overcoming Cardiff City last time out. In came McAteer, replacing Wanya Marçal. The system remained the same, with Ricardo Pereira tucking into midfield on occasions, while Wilfred Ndidi pushed forwards out of midfield. Before kick-off, both sides took the knee to reaffirm a commitment to eradicating discrimination of all kinds from the game. From the off, the locals had the voices of the travelling Blue Army ringing in their ears - 2,205 of them - singing of City playing football 'the Enzo way'. It's been a hugely positive beginning to a campaign City hope will end in promotion.
It was a dramatic start in Rotherham. The visitors thought they were a goal down inside the opening 10 minutes when Jordan Hugill used his upper arm to divert Cameron Humphreys' header into Mads Hermansen's net. The linesman had spotted it, however, and after a short consultation with referee Simon Hooper, the goal was chalked off. Within a flash, the Foxes were ahead. The move was typical of their start to the new season. Tidy play between Stephy Mavididi and Kelechi Iheanacho afforded the latter with the room he needed to pick out a cross to McAteer. The youngster did the rest, nodding in at the far post, practically on the goal-line.
McAteer drilled wide in pursuit of a second moments later, before Cafu headed over for the home side. The two teams traded blows and it was a relatively even contest at the break. Matt Taylor's Millers were clearly up for the fight. They weren't giving City a great deal of time to build any forward moves with. They were making it a battle - especially in the second half. Their reward was a levelling goal eight minutes after the interval. Andre Green's floated ball into the box was exactly what they needed to carve City open and there was Luton Town loanee Onyedinma to glance his header into the bottom corner.
The complexion of the game had changed. With Rotherham coming at them, Leicester had defensive work to do. A smart stop from Hermansen frustrated Hugill just after the hour, although the offside flag was also raised. Kiernan Dewsbury-Hall's long-range drive was deflected behind from 20 yards later on, before Ndidi's header flew over the bar. City were being made to work for it once again in the second tier, but another late winner was on the horizon. Callum Doyle's diagonal ball was hopeful but also exceptional - evading Cohen Brammall and putting McAteer clear to belt it through former Leicester 'keeper Viktor Johansson's grasp. The away fans went ballistic - toasting another last-gasp winning moment by chanting McAteer's name.
There's a long way to go, but things are looking up for the table-topping Foxes. After Tranmere Rovers away in the second round of the Carabao Cup in midweek, it's Hull City at home next up in the Championship before the international break.