Saka has just returned from long-term hamstring, with his absence coinciding with Arsenal's Premier League title challenge collapsing.
Maitland-Niles, who left Arsenal last year for OL, told BBC Sport: "I think they now rely on him a bit too much and you can't expect so much from such a young player.
"He hasn't even hit his prime yet. But I think he is the driving force of the team and they miss a bit of attacking threat when he is not playing.
"Bukayo has become one of the world's best wingers, very consistent, knows how to kill off a game and he can pick his moment in a genius way."
On 18 year-old Ethan Nwaneri, he also said: "Physically, he is absolutely incredible and there is no fear in the kid.
"He is just going at people and trying to make things happen. You can see he is trying to become a leader very early in that team. He is trying to cement his place which is difficult as he plays in the same positions as (Martin) Odegaard and Saka.
"But he has got the ability to do so as well. He has the world at his feet and he just needs to take his chance."