The Belgian's durability was called into question this week following a series of premature withdrawals with seemingly minor knocks.
Mirallas told evertontv: "It is the manager who decides how long you stay out on the field but he is leaving me out there more and more for longer in each game and I think he can tell I am feeling fitter and lasting more into games now.
"I am quite pleased with my own form. I think I am playing quite well. I had a decent game - I would have liked to have scored but you can't score every game and Tuesday is another opportunity."