Jackson, 33, broke into the bigs in 2003 with the Los Angeles Dodgers. He spent three seasons with the Dodgers before being traded to the Tampa Bay Devil Rays in 2006.
He was shipped to the Detroit Tigers in 2008, where he posted a 13-9 record and 3.62 ERA, making his only All-Star appearance. He was traded again in 2009 to the Arizona Diamondbacks. The next season he was traded to the Chicago White Sox. In 2011 he was traded to the Toronto Blue jays. He was traded later that season to the St. Louis Cardinals, where he won a World Series.
Jackson had his first stint with the Nationals as a free agent in 2012. He signed again as a free agent in 2013 with the Chicago Cubs. That deal was for four years and $52 million, but resulted in a league-high 18 losses and a 4.98 ERA.
He posted a 7.20 ERA in three appearances this season for the Orioles, allowing 11 hits and seven runs in five innings. Jackson posted 3.10 ERA in 20.1 innings for the Norfolk Tides, a Triple-A affiliate of the Orioles. He owns a career 4.65 ERA and 93-114 record as a starter in 15 seasons.