Boston entered the off-season with a packed 40-man roster. Even after they lose some players to free agency, things are still tight, hence the Red Sox designating Che-Hsuan Lin for assignment when they picked up relieverSandy Rosario off of waivers. There's always the concern that a designated player will be claimed by another team, and for Lin, that club is the Houston Astros.
Lin used to be more of a prospect, with Baseball America rating him in Boston's top 30 four separate times. However, they haven't ranked him in either of the last two years, as his production plateaued. The Astros have a serious lack of talent on their 40-man roster, though, as they try to rebuild both in the majors and in the minors. Players like Lin who might have a use will likely be picked up by the Astros this winter -- look out for them at the Rule 5 draft, for instance -- so it's not surprising to see him gone that way.
Lin isn't much of a hitter, as he solved Triple-A Pawtucket, where solved for Lin means he hit .247/.323/.316. However, he's a fantastic defensive outfielder with a strong arm, and on the right roster, could be useful as a bench outfielder and pinch runner. Boston has plenty of other outfield options, with more coming up, but the Astros can afford to see just what Lin is going to be. Much like they could bother with Jed Lowrie and Kyle Weiland, two Boston players they acquired last off-season.
Lin is often compared to another light-hitting Boston prospect, Jose Iglesias, in the sense that his bat won't let him flourish in the majors. There's a major difference, though, and that's the fact Iglesias plays a position where terrible offense is the norm -- replacement-level offense from a shortstop is much different than for a center fielder, so Lin has far less slack to work with in his production. Used appropriately, though, he can be worth a spot on the bench for a team in need of defensive help in their outfield.