With Russell Martin signing with the Blue Jays, the trade market for Miguel Montero just took a big jump. The Blue Jays weren't thought to be a likely destination, leaving several teams still in the market for an improvement at the position. Chief among them are the Cubs, with the Dodgers up there. The Pirates, with Francisco Cervelli signed, would probably not be in the market.
That leaves the Cubs, basically, because the likelihood of a trade with the Dodgers just isn't very good. The Cubs do have some prospects that would generate some interest, like Paul Blackburn or Carson Sands. Neither of them would be able to contribute in 2015, but they might join the rotation going forward, and a team can't have enough pitching prospects.
But who would replace Montero in that situation? This is where a three-team (or more) trade might come into play. With the signing of Martin, the Blue Jays might not have a place for Dioner Navarro, who certainly isn't as good as Montero defensively, but is good offensively. He's also due 5 million compared to Montero's 12 million. Since the Jays might also be looking to save some money, I could see them looking to deal Navarro. The Cubs can afford to take on Montero's salary. The asking price for Navarro shouldn't be too high, as he's only under team control for another season. Could the Cubs and Blue Jays be persuaded to a deal that sends Montero to the Cubs, a prospect to the Jays, and Navarro and a pitching prospect here?
I'm not real familiar with the Blue Jays farm system, so I don't know what prospects they might need, but the Cubs are probably looking to deal, and Stewart and company should probably be moving forward on that.