Andrew Miller is headed to Baltimore.
Miller, a veteran lefty in his ninth big league season, has been one of the premier left-handed relievers in the AL East over the last two seasons, and he's in the midst of a career year. His 2.34 ERA and 0.898 WHIP—both career bests—trail only Koji Uehara's 1.48 and 0.74 marks on the Red Sox this season.
Rodriguez, Baltimore's No. 3 prospect according to MLB.com, has struggled in Double-A this season. He's 3-7 with a 4.79 ERA across 16 starts.
The Sox, who trail the Orioles by 13 games, have made it clear that they're focusing on a rebound season in 2015, trading away starters Jon Lester and John Lackey earlier on Thursday. The acquisition of Rodriguez is another indication of that mindset, though the prospect will have to prove his ability to pitch in the upper levels of the minors.
Since going to Double-A in 2013, Rodriguez is 7-10 with a 4.55 ERA, and he could project as a middle reliever if his stuff doesn't prove to measure up against top competition. Either way, the Orioles snagged a proven reliever for a prospect who has stalled in the minors, and they appear to be frontrunners for the AL East crown.