Presumed Plan : Ian Desmond starts at SS. Danny Espinosa, starting or backing-up 2B, backs him up.
Reasoning on Presumed Plan : In 2012 & 2013 Ian Desmond was arguably the most valuable SS in the major leagues. In 2014, he dipped noticeably and is probably now... the third or fourth most valuable SS in the major leagues.
Ian corrected his error prone ways of a few years ago and plays consistently good defense. He has always hit for power and still does especially for a SS. Specifically he has HR power something rare for the position. (Ian's 24 homers led all SS and were 7 more than 4th place on that list, 9 more than 5th). He might have lost something average wise but he has brought his patience up from OMG NO to barely acceptable to help compensate for that. All in all he's a good player in a position where it has become easy to find an ok player but is still hard to find good ones. It's an easy call.
Ian also plays all the time upping his value. He's missed 12 games in the past 2 years, and has played at least 154 games in 4 of the last 5 seasons. His back-up hardly matters but Espinosa, who came up the ranks as a SS, still plays the position well enough to cover on the rare off days for Ian.
Problems with Presumed Plan : As you can tell from the above there aren't many problems with the plan here. I can think of two. The minor one is that Ian appears to be slipping offensively. His strikeout percentage went way up from say ~21% during his 2012-2013 peak to over 28%. It's not an issue of judgment. His swing percentage for pitches outside the zone is consistent with last year. He's just not making contact on those pitches. In fact contact on pitches outside the zone has dropped every year since 2011 from 65.5% now down to 53.5%. We'll have a specific Ian post sometime later in the off-season but the gist of the problem is the size of the zone where Ian can hit a ball has shrunk. It's not a big problem right now. His zone was rather large before so the shrinkage hasn't made him a bad hitter just no longer a good one. But if it shrinks further then we might have a problem. And it will shrink - time gets to all men - the question is when.
The major problem is that Ian is up for free agency after next year. Ian is the type of player (high value at an important position, but heading into his 30's and ready for a big payday) that you LOVE to trade, but the Nats can't really do that. They have no acceptable back-up plan. They are a win-now team that needs a successful Desmond to be as good as they can be. Given that, the Nats are forced into a very difficult position of having to decide on a re-signing a player whose potential value over the next 5 years swings wildly. You love to avoid those type of coin flips. The Nats can't do that.
My take : Starting Desmond is a no-brainer. There's not only is no better option internally, it's hard to find a better option externally. As down as we may have been on Ian, his combination of power and defense makes him one of the best SSs in the majors. Plus, most of his competition is older. Peralta? Older. Aybar? Older. Rollins? Way older. Hardy? Hanley? Alexi Ramirez? Reyes? All older. Outside of Alcides Escobar, who as a true singles hitter has a value very dependent on his BABIP, Ian is a good year and a half younger than anyone close to his value. (And he's closer in age to the younger Escobar than any of the others, I think). Do I think he's slipping? Yes. Do I think it matters for 2015? Not even close to enough to question starting him.
The long-term deal is an issue and a tough one but that's neither here nor there when it comes to what to do at SS this year. The Nats can't deal Desmond without getting a good SS back. That isn't going to happen so he plays and they either work it out or they don't.
As for Danny as the back-up, Ian plays so many games that it hardly matters who backs him up. Yes it is an issue if Danny is your starting 2B and Ian goes down with an injury. The drop off will be devastating. But there are bigger fish to fry when it comes to finding a good back-up for a Nats player who might get injured.
Outside the Box Suggestion : You know who doesn't have a SS and is desparate to win now? Detroit. The Tigers are facing a big offseason where they could start to rebuild. They very well may lose Martinez, Scherzer, Hunter, and some pen pieces. But really 2016 looks like the better rebuilding year. You still have Price, Porcello, Nathan, Davis, Soria, and Avila now but maybe not after 2015. So it makes sense that they make another last gasp attempt in 2015 before trying a quick rebuild. How best to do that? Well trading for a contract that expires after 2015 and giving up a contract that lasts until 2017 helps. A challenge trade of sorts; Desmond for Kinsler. Ian for Ian. Sure that gives DET an issue at 2B but that's an easier position for them to fill as they were already shifting their best minor league hitter from 2B to OF to get him up to the majors. Now they don't have to.
Why would the Nats do this? Well Kinsler's contract fits the Nats window better. The Nats face the Tigers 2014 and 2015 offseasons a year later. They could look to do a quick rebuild after next year (ZNN, Fister, Desmond, Span, and Clippard can walk after 2015), or they could hold it off until after 2016 (when Stras, Ramos, & Storen might leave and the Nats can let Gio go if they want). With Kinsler instead of Desmond you make it an easier decision to try to keep that window open, removing one of those 2015 FAs. Plus Ian has a nice deal where the back end actually drops in price. He's paid 16 million next year, but 14 in 2016 and 11 in 2017. This gives the Nats more flexibility payroll wise than a re-signed Ian.