I thought this answer from from Blue Jays GM JP Ricciardi was interesting. He refuses to name names, but the timing fits the supposed Rios trade from a couple season ago (if so, it means that the Giants had agreed to the trade):
"But I had a trade done a couple of years ago where the trade was finalized, I won’t mention the players, but a pretty prominent player. Had him traded, everything was all set, told the president this is what we are trying to do, kept him in the loop. I went back, already signed off with the team, I said, I’ll just get right back to finalize, let me run it by my president.
I went and told the president and the president told me, You know what, I’m a really big fan of that guy, and I think the fans are, too. I think if we trade him, we’re really going to catch it. And I said, OK, it’s your call. I said I recommend we do this, but he said no, and we didn’t trade him and the guy we could have traded him for is absolutely tearing it up right now. So, that’s why you can’t be a fan when you make those choices.".