After injuries forced the Twins to simply give Span a shot at the major league level, he surprised everyone by hitting .294/.387/.432 in 93 games, with his plate discipline improving substantially at the big league level. In 2009 he quieted any "fluke" talk by hitting .311/.392/.415 in 145 games, and it appeared the Twins had found their lead-off hitter for years to come. The Twins were impressed and decided to lock Span up long-term, and he's making $3MM this year, $4.75MM next season and $6MM in 2014, with a $9MM team option for 2015. That's a very team friendly deal for the kind of outfielder Span was his first two seasons in the majors.
However, Span's offensive contributions have largely disappeared dating back to 2010. He hit just .264/.331/.348 in 153 games that year, and then basically matched that line in half as many games last season when he hit .264/.328/.359. He's been a little better this season, as he's hitting .291/.359/.358, but the fact that his power is largely disappearing is a cause for concern. His slugging percentage is down more than 20% since his 93-game rookie campaign, and has been trending downward each year.
It's hard to know for sure which Span the Twins will have for the next few seasons, although it would appear he's trending in the wrong direction. His walk rate and line drive percentage has been basically the same dating back to 2010, so it's unlikely that he's dealing with simply bad luck. Whatever it was that made Span so effective for his first two seasons in the big leagues seems to be missing from his game these days.
Last season while Span was dealing with a potentially serious concussion, the Washington Nationals still expressed interested in adding Denard. The rumored deal was centered around closer Drew Storen and apparently fell apart when the Twins asked for infielder Steve Lombardozzi as well. That interest suggests that Span still will have some suitors if the Twins do indeed decide to trade him.
Considering the team is 14-27 and has a lot of young outfielders that need to be given a shot, I think it's in the team's best long-term interests to trade Span. While I would prefer the team get more than an overvalued late-inning reliever for him, I certainly wouldn't complain if that's the deal they ultimately made. Storen for Span might be discussed again this summer, as Storen's coming back from surgery himself and the Twins will undoubtedly want to see him throw again before pulling the trigger on any kind of deal.
If both players can remain healthy through June, don't be surprised to see discussions heat up once again. That would allow the Nationals to play Bryce Harper at one of the corner outfield positions, where they feel more comfortable with him.