NBC will be covering both games, which means you can legally watch them online through NBC Sports Live Extra. The Saturday games will be carried on NBCs mobile app as well, which is also used to stream Sunday Night Football.
NBC is one of the few national networks that has fully embraced online sports viewing. Besides its SNF coverage, it has every Premier League game available online to subscribers and plans on expanding the service during the 2014 Winter Olympics in Sochi.
On Sunday, the games shift over to CBS and FOX, who will also carry the Divisional round and AFC and NFC Championship games. CBS will provide free streaming of the Chargers vs. Bengals game at CBSSports.com. FOX will stream 49ers-Packers through FOX Sports Go, but you'll need login information for Comcast, Cablevision or AT&T U-verse to watch.