As noted at MLBTR, Korean closer Seung-Hwan Oh is looking to move to MLB. The 33-year-old Oh is a free agent and so is not subject to the posting system. According to MLBTR, the Pirates, as well as the Yankees, Orioles and Mariners, are known to have scouted Oh. Of course, that doesn't mean the Pirates would be interested in him, especially as an unrestricted free agent.
It's pretty hard to see Oh stepping into a closer's job and I can't specifically see the Pirates signing him with that intention, at least not right away. They need another late-inning reliever, though, to replace Joakim Soria, and who knows what the future holds as Mark Melancon gets more expensive and moves toward free agency. Oh's stats can be found here. They're obviously impressive, including a career K/9 of 10.7. Oh is only 5'10", but that's taller than Marcus Stroman.