One of the many rumors that popped up during the trade deadline had the Minnesota Twins sending Denard Span to the Washington Nationals for closer Drew Storen, outfielder Roger Bernadina and minor leaguer Stephen Lombardozzi. Thankfully that didn't happen.
The Twins do have a glaring weakness in the bullpen but you just don't trade an above average center fielder for a closer. Since Span arrived on the big league club in 2008 he has posted a WAR of 12.6. By year it has looked like this: 2008 3.2, 2009 4.1, 2010 2.6, 2011 2.6. This year Span should post at least a 4.0 WAR, if he hadn't gotten hurt he could have been looking at a 5.0 WAR. League average WAR is 2.0, Span is putting up above league average.
Being a leadoff hitter one would expect Span to post an above average OBP and Span does just that. So far this year he's getting on base at a .361 clip which is pretty much right at his career norm. He also posts a very low K%, striking out only 10.2% of the time. He does exactly what you want your leadoff hitter to do.
Besides being a solid leadoff guy Span is also solid in the field. Since 2008 he has posted UZRs of -3.2, -5.4, 4.4 and 9.9. Traditionally it's best to look at UZR in 3 year intervals but as you can see he's turning into a quality defender as he enters his prime.
I haven't even talked about what makes Span so valuable though. It's that very team friendly contract he signed last year. The contract was for 5 years $16.5 million with a 2015 club option. That's about as team friendly as it gets. This year alone Span has already been worth $11.9 million dollars. 1 WAR is worth roughly $5 million dollars. Through the life of his deal let's say he reaches a 3.5 WAR in 2012, a 4.0 WAR in 2012, a 3.5 WAR in 2013 and a 3.0 WAR in 2014 he should be worth roughly $75 million dollars. Geez, talk about team friendly. The Twins signed him for $16.5 mil and he could potentially be worth $75 mil when his contract is up.
You can see why Span is so valuable to the Twins.
There's not much to say about Storen. He's a reliever. Relievers are a dime a dozen. He's put up .2 WAR this year, has a 3.84 FIP, a .228 BABIP so his ERA will see an increase. It's currently at 2.87. There's not really much to write about. Lombardozzi is a solid prospect who's hit very well in the minors but he doesn't justify trading an above average center fielder/leadoff hitter. Bernadina is just meh.
Edit: I forgot to mention that the Phillies got Hunter Pence from the Astros for 2 top prospects and 2 mid-level/lower-level prospects. Since '08 Span has produced only .9 WAR less then Pence. Span easily can bring in more then that measley offer the Nats gave.