Storen, 26, had a 4.52 ERA (84 ERA+) with a 3.05 K/BB in 61 2/3 innings this past season while spending some time in the minors. He saved 43 games with a 2.75 ERA (140 ERA+) as recently as 2011, but had elbow surgery prior to 2012. There is some belief the Nationals have soured on Storen over the last year or so.
The 26-year-old Espinosa hit an awful .158/.193/.272 (27 OPS+) in 44 games this season before being sent to Triple-A, where he hit .216/.280/.286 in 75 games. He has played through shoulder and wrist injuries in recent years. From 2011-12, Espinosa hit .242/.319/.408 (97 OPS+) with 38 home runs and 37 stolen bases while playing second base and shortstop.
After adding Doug Fister and Nate McLouth, the Nationals don't have much shopping to do this winter. Beefing up their bullpen and bench is the only real pressing item, so trading Storen and Espinosa doesn't make sense in that regard.