Zach Stewart isn't the only recently designated pitcher sent away from Boston in a trade today, as Sandy Rosario is now an Oakland Athletic following Wednesday's swap for yet another player to be named later or cash. Rosario was claimed by Boston earlier in the off-season when the Marlins put him on waivers, and now Boston, after putting him on waivers themselves, sent him packing to Oakland before he ever threw a pitch in a Red Sox uniform.
As with any designated player, there's a limit on how long a team has to perform their next move with him. Rosario could be traded, as he was, or he could simply be outright released or sent to the minors, most likely Pawtucket. Boston chose to ship Rosario and his remaining option off of the roster, and like with Stewart, it's unknown what the return is at this point. Also like Stewart, it probably won't be much.
Rosario had a high-velocity four-seamer, but he threw it a little too straight for use in the majors. While progress has been made on his two-seamer, apparently there wasn't enough to justify keeping him around in Triple-A to wait and see. At least, maybe not on a roster as loaded with relief options as Boston's, anyway. In Oakland's expansive park, they might find the case to be otherwise.
Danny Valencia has also been traded, but not for a player. The Baltimore Orioles sent cash considerations to the Red Sox, according to the Baltimore Sun's Dan Connolly. Valencia, unlike Rosario, actually played for Boston, but didn't log much more playing time than nothing. He totaled just 10 games and 29 plate appearances, spending most of his time in Triple-A with the PawSox instead. Valencia didn't impress much at either level, and while he's a former prospect with one solid year in the bigs under his belt, there's not much reason left to hope given his last two years in both the majors and minors.
He was originally acquired from the Twins for minor leaguer Jeremias Pineda in early August, and it made sense at the time, given Boston was looking for infield depth. Things have changed since, though, and Valencia was also designated last week in order to make room to protect other players from the Rule 5 draft. It's very likely none of these three would be selected in that, but they are almost all superfluous pieces in the Boston organization, so trading them post-designation isn't a surprise.