I had thought this was a done deal, I guess I was wrong. According to
Jon Heyman, the Sox and Gonzalez couldn't come to an agreement on a contract extension which led to Boston pulling out because they were unwilling to trade Casey Kelly, Anthony Rizzo, and Reymond Fuentes to get Gonzalez for just one season.
The teams can still negotiate a deal, so stay tuned. But for now Gonzalez remains in San Diego.