Looks like Seo was traded for Sanchez. The trade as reported by the AP:
The Los Angeles Dodgers, in search of starting pitching, acquired right-hander Jae Seo and left-handed reliever Tim Hamulack from the New York Mets on Wednesday for right-handed relievers Duaner Sanchez and Steve Schmoll.
Hamulack will be 29 next year, so he's not much of a prospect. Schmoll will be 26 and just got his first taste of the majors last season and posted a 5.01 ERA. He doesn't look like anything but a back-of-the-bullpen reliever at this point.