The good thing is a broken fibula is usually good within 2-3 months, from what I'm reading injuries like his he can put weight on them and can start rehab training on it around 6 weeks. Should be nothing serious and he'll be ready to go next season.
Maybe the Raiders can be like the 1990 Giants and McGloin can be like Jeff Hostetler and lead the team to glory like when he came in for Phil Simms in time for the playoffs after Simms got injured at the end of the season lol