It's not a direct comparison, WAR was used to point out just how terrible an idea that is because Kyle Gibson has been really, really good and continues to improve as the season progresses. Is Kyle Gibson more valuable than Tulowitzki in 2015? I'm far from certain that's the case. Is Kyle Gibson at $500k more valuable than Tulowitski at $20m? Hell yes. That's not even in doubt. To give up a good cost-controlled player who is contributing today for an older expensive player who may or may not contribute more wins to the team is the kind of deal that gets general managers fired, and for good reason. It's idiotic. And then you get into the fact that Tulowitzki has a pretty extensive injury history and has crossed the age of 30. There isn't a situation where you can paint that trade idea in a positive light. Tulo is a "win now" move. It's damned near impossible to "win now" when you give up a younger, possibly equal value, player in trade for that older, expensive player. Gibson could actually get better from 2016-2018. It's unlikely but it's possible and it costs the Twins very little to find out. On the other hand, you can pretty much bank on Tulowitzki diminishing in some capacity from 2016-2018. It has already started to happen. His fielding metrics are no longer impressive and haven't been for several years.