How do you debug MVC 4 API routes?

I have a WP7 game that uses RESTsharp to communicate with my MVC4 RESTful server, but I often have issues making requests that work and therefore I want to debug where it fails.

This is an example where the Constructor on my GameController is hit, but the Post method is not hit, and I don't understand why.

Client code:

public void JoinRandomGame()
{
  client = new RestClient
  {
      CookieContainer = new CookieContainer(),
      BaseUrl = "http://localhost:21688/api/",
  };

  client.Authenticator = GetAuth();

  RestRequest request = new RestRequest(Method.POST)
  {
      RequestFormat = DataFormat.Json,
      Resource = "game/"

  };

  client.PostAsync(request, (response, ds) =>
  {});
}

Server code:

    public void Post(int id)
    {
        if (ControllerContext.Request.Headers.Authorization == null)
        {
            //No auth
        }
        if (!loginManager.VerifyLogin(ControllerContext.Request.Headers.Authorization.Parameter))
        {
            //Failed login
        }

        string username;
        string password;
        LoginManager.DecodeBase64(ControllerContext.Request.Headers.Authorization.Parameter, out username, out password);
        gameManager.JoinRandomGame(username);
    }

My routes are like this

       routes.MapHttpRoute(
            name: "gameAPI",
            routeTemplate: "api/game/{gameId}",
            defaults: new
            {
                controller = "game",
                gameId = RouteParameter.Optional
            }             
        );