The left-hander posted an ERA of 3.29 in 2012 for the Rangers, doing so over the course of 213.1 innings pitched that spanned across 32 starts.
He has been an important part of the Rangers' recent success, pitching 185.1 innings in 2011.
The 27-year old was drafted in the third round out of a high school in Durham, North Carolina in 2003 by the Atlanta Braves. He was traded to Texas as part of the now-famous Mark Teixeira-trade that sent the first baseman to Atlanta.
With a little over 4 years of service time, this extension will buy out 3 years of his free agency at roughly $11 million per year. Texas has also recently signed Derek Holland to an extension, as the club continues to show a commitment to locking up its young core of players.