Nats want Mike Leake
What Mike Leake is, is young (turned 28 about a month ago), durable, and a starter with limited wear and tear. As far as good bets to give you what you expect for the duration of a contract go, Mike Leake is about as good a bet as you can make. What you expect, though, may vary. He's had fairly average results and the fancy stats that back that up and suggest he might have even been lucky to be average. He doesn't do anything particularly well, but nothing particularly poorly. If you like him, think maybe he can get a bit better, you've got a #3 type pitcher for the next 5 years. If you don't like him, think he might lose that luck as he passes over his peak, then you've got a #5 type. But like I said - you've likely got him for 30+ starts a year which is more valuable than we give credit for.
Nats sign Yusmiero Petit
With Petit you get a Craig Stammen type. Middle innings, reliable, former starter so can go multiple innings. You also get Craig Stammen costs though as he comes at 2.5 million. But he's Craig Stammen 2014 (ok), not Craig Stammen 2012-13 (very good!), or at least that's the best guess of what he is. Petit has wavered between starter and reliever since coming into the league. Perhaps with a focus on relief for a few years he will blossom. Perhaps. All the Nats are really looking for with Petit is average, consistent innings. Don't blow up in big spots. He's been in his share in SF and he's been... average! So good.
Mets get Walker for Neise
Makes the Mets better than they were a day ago. Walker has more patience and power than Muprhy (don't let the post-season fool you on Muprhy's power) but Murphy is a better pure hitter, making more contact and hitting 30-40 points higher than you'd expect from Walker. That is enough to even out any difference. Walker is a better fielder but in the "Murphy is bad, Walker is not bad" way. Neise is a fine pitcher. If you buy into last year than it's probably a bad deal for Pittsburgh, but if you think he's more like previous years, or even in-between than the Pirates get their own Mike Leake, with two team options to keep him on the team. For the Nats it makes their current rival a bit tougher than the day before, but it's not the big move we're worried about.
Mets sign Asdrubal Cabrera
You know Asdrubal. He's ok! He can hit ok, and he's not terrible in the field. Is he better than Wilmer Flores? Yes a little. If it's just a little why bring him in? Well, Flores did just break a bone and if you don't bring someone in and he suffers a set back the Mets are back to having the black hole of Ruben Tejada hitting. With this and the Walker deal the Mets haven't made themselves any better per se, but they've set up a situation where its hard to see them being terrible again on offense without massive injury issues. (thosse do happen!)