
Rosenbaum, 25, was selected by the Rockies in December's Rule 5 draft and was making a bid to crack their Opening Day roster. He allowed four runs in eight innings of work this spring, but Colorado's late signing of veteran right-hander Jon Garland ate up the last available spot on the pitching staff and made Rosenbaum expendable.
Per Rule 5 regulations, the Rockies were required to pass Rosenbaum through waivers and then offer him back to the Nationals for $25,000 (one-half of the original cost to draft him). The Nationals elected to re-acquire him and plan to have him join the rotation at Class AAA Syracuse to begin the season.
A 22nd-round pick in 2009 out of Xavier University, Rosenbaum