You need to complain to Marquee Sports Network. THEY have to make their app compatible with the Chromecast with Google TV interface in order for it to work directly. Google gave every developer the ability to do this so that Google would not have to be involved and slow the process. That's why there are literally 10s of thousands of cast enabled apps.
I think you will see more urgency for some of the stragglers like this one now that Google has moved so strongly into this format and has stopped making the older no-interface Chromecast devices.
