Matt Harrison is a 29-year-old sinkerballer. The Braves took him in the third round in 2003, and by 2007 he was ranked as their third best prospect. This is why he was included, along with Jerrad Saltalamacchia, Neftali Feliz, Beau Jones, and Elvis Andrus in a trade with the Braves for Mark Teixeira and Ron Mahay on the day of the 2007 trade deadline.
So he is no stranger to being included in these mammoth deadline deals, though before, he was a bright, up-and-coming "maybe" whom the Rangers desired.