For digital TV startup Aereo, the road to growth has been a difficult one. And it's not getting an easier.

Actually, the four major broadcasters that are suing Aereo over the startup's ability to provide digital streams of broadcast signals have a lot to lose, too. Many programmers who provide valuable primetime content have already said they’ll move their shows to paid cable networks if Aereo prevails in court.

Now, Major League Baseball and the National Football League seem to be of the same mind.

In a document called a "friend of the court brief" which has been submitted to the Supreme Court, the leagues argue that what Aereo does is a violation of their "exclusive retransmission licensing rights."

"Those stations will become less attractive mediums for distributing copyrighted content," the brief says. "The option for copyright holders will be to move that content to paid cable networks (such as ESPN and TNT) where Aereo-like services cannot hijack and exploit their programming without authorization."

Related: Digital TV Startup Aereo May Wind Up in the Supreme Court

The four broadcasters that are suing Aereo are ABC, CBS Broadcasting Inc., NBCUniversal and Fox Television Studios.

In order to carry major league sports, cable and satellite providers pay $300 million in "compulsory" licensing fees, about $100 million of which goes to the leagues.

If Aereo wins, it’s still not clear how quickly the NFL and MLB could yank their programming.

Aereo, a service that allows users to stream live TV over the internet for a small monthly fee, has been embroiled in a legal battle with the four major broadcasters that’s gone all the way to the Supreme Court.

The broadcasters argue that Aereo is stealing copyrighted content. But Aereo, which does not pay the broadcasters, argues that it isn't doing anything that individuals couldn’t do themselves with their own antennas.

In several other cases where litigation is pending, courts have denied broadcasters' requests to make Aereo cease its operations until a decision is reached.

Related: 7 Technologies That Are Disrupting the Cable TV Business