As described in Step 25 (The Main Character), the protagonist is one of the most misunderstood characters in a story's structure. It is often assumed that this character is a typical "Hero" who is a good guy, the central character, and the Main Character.
In fact, the protagonist does not have to be any of these things. By definition, the protagonist is the Prime Mover or Driver of the effort to achieve the goal. Beyond that, he, she, or it might be a bad guy (such as an anti-hero).
Being the central character just means that character is the most prominent to the audience. For example, Fagin in "Oliver Twist" is perhaps the most prominent, but he is certainly not the protagonist. So, a protagonist may actually be less interesting than the antagonist, or may even be almost a background character.
And as we have already explored, the Main Character is not always the protagonist, but could be any one of the characters in your novel who represents the reader position in the story.
So, the only attribute you should consider in refining your protagonist is to ensure this character is the one with the most initiative toward reaching the Goal.
Referring to your cast list, your plot synopsis and your story synopsis, confirm that the player you chose as your protagonist is still the best person for the job. If not, choose the player that is.
Then, taking into account all the plot elements you have added to your story in recent steps, write a short description of how your protagonist is crucially involved in your plot as its prime mover.