In that case, you can create a separated project using ASP.Net Web Api.
Using Web Api, you should be able to inject your services into your controllers and call those Rest Services from your MVC application as well as from any other application (mobile, etc).
You can also consider, in case you are using EF, creating a separate project(layer) for your repository and inject the
EF Context into your repositories, the repositories into your services layer and your services into your controllers.
In my personal projects, I call the services layer only from my WEB API project and never from my MVC application. The MVC will use the services layer only through your REST Services.