As for Nick Green and Jed Lowrie -
Nick Green was a spotty fielder at SS. Between Lugo and Green, and a few innings to Lowrie and some AAAA types, the Red Sox had about the worst rated SS defense last year before they brought in Alex Gonzalez. Green has a cannon for arm, but it is like one of those unrifled cannons that shoot shells with extreme inaccuracy. Having said that from memory, I checked his UZR ratings on Fangraphs and what it suggests is that he has decent range at SS and an ability to start/turn DPs which gave him a slight positive fielding value at SS last year. Still, the sample size (750 innings and < 300 chances handled for his career would make me say "small sample size" and not even trust the range numbers. As for 2d, he's had double the amount of innings over his career and is less than run below average. As for his bat, it was bad enough after June last year that the Red Sox felt it was a need to get him out of the line up. My bottom line on Green is he is a middle infield back up who gives you nothing special off the bench. I do not see him as a starter for a season, but he can fill in well for a month or so. Really an AAAA player not worth more than MLB minimum. With Desmond and Espinosa, I would rather see them play if there is need for a one month fill in. I'd rather play Willie at 2d as a backup and get a corner infielder as the last bench bat.
Lowrie, on the other hand, is much more interesting, but he would cost you more. He is likely to start the year in Pawtucket to get innings in, if he is not a piece of an Adrian Gonzalez or Miguel Cabrera trade. His wrist was not right last year and required two surgeries (before the season and in April). He has a very good defensive reputation, so good that he was shifted to SS from 2d in the minors. His bat is supposed to be MLB average, which is good for a plus defender in the middle infield. I do not see the Sox giving him up cheap, but I could see them moving him because they have a lot of SS depth a year or two away (including Iglesias, who had a decent AFL and is an MLB fielder already). Sox and Nats do not match well for trades because the deepest positions in the Red Sox organization are catcher, SS, and CF, and they have a number of arms for fill in roles at high levels and upside at low levels. If there were a power prospect (Marrero? Burgess?) then there might be something to talk about.