The Denard to the Nationals rumors refuse to die, and with the Twins looking like they will not be competing in the next 2-3 years. I think maximizing Spans trade value and dealing him in the next month might be the right thing to do.
Now what type of package could we expect to get from Washington has been of of much debate among fans. I have seen some suggest that anything less the Jordan Zimmerman is a deal breaker and others who have clamored we still look for a package revolving around a closer. I thought a good starting place would be to see what other players of Span's caliber have been moved for in recent years and then try to find the best package based on that estimate.
The most logical starting place to me was the Michael Bourn trade last year between the Astros and Braves. Atlanta sent a young, low ceiling major league player and 3 minor leaguers none of whom where top prospects to acquire the leadoff hitter they needed. Bourn was worth 14.0 WAR from 2008 through 2011 while Span was worth 12.2 but missed half of 2011 with his concussion. They are similar players and feel Span should be able to return similer value.
In terms of a low upside major league ready player, I would ask for Steve Lombardozzi who is basically a younger version of Jamey Carrol and could be a useful 2B for the near future not to mention his ties to Twins history. In terms of prospects coming back in the deal I think it is unreasonable to expect the Nationals top prospects as much as I would love to see Anthony Rendon despite his health risk.
When looking through the rest of the Nats top 20 prospect lists they have some pitchers who intrigue me but unfortunately they are hurt or have major question marks about them. Sammy Solis is a 22 year lefthander who sits 90-94 with a plus curveball and solid change, but he is out with Tommy John for the year. Robbie Ray is another young lefthander with three solid pitches, but lacks the upside of some of the other arms in the system. A wildcard Lefty is Kylin Turnbull who has the size and fastball to be an ace but has yet to develop the secondary pitches or consistency. Matt Purke has shoulder issues, Alex Meyer may never be consistent enough with his mechanics to start and so on...
With that in mind I would start the negotiations with Span for Rendon straight up. Twins get their 3B of the future and the Nats fill a big need with a solid CF and very good leadoff hitter as they make a run this year.
Assuming the Nats would balk at giving up Rendon, I would counter with an offer of Span for Lombordozzi, Ray, Turnbull, and PTBNL with the expectation that the player would be Solis assuming he medicals come back positive at the end of the year. The Twins get a young, high OBP, solid defender at 2B to pair with Dozier until Michael is ready. They also get Ray and Turnbull as minor league pitching depth while still being a couple of years away. Getting Solis as the PTBNL is the key to the deal in my opinion. Assuming he does not have any setbacks during rehab, he should be ready to pitch by next spring since he had surgery in Feb. He was set to be at AA so he could conceivably be major league ready by 2014 and profiles as a #3 starter who can miss bats. Something the Twins sorely need.
I think this is a realistic idea of what a return on a Span trade could look like and you could see by 2015 a starting 2B a #3 starter, a #4 starter, and a solid bullpen arm (if Turnbull cant develop secondary pitches) for a year and a half of Span. That's a good value in return.