Greene was promoted from Triple-A Gwinnett before Sunday's game against the Dodgers. Greene signed a one-year contract with Atlanta on May 9 and spent the most of the month getting ready at the team's extended spring training facility before coming to Gwinnett. He made his major league debut that day as a defensive replacement in Los Angeles' 7-6 loss to the Cardinals. The 27-year-old left-hander went 2-1 with a 3.18 ERA (30 ER/82.1 IP) over five minor league seasons with San Diego, Oakland, and Washington before being released last July. He returned to the Nationals this past August after signing with them as a free agent following the season. In 21 relief appearances for Washington, he was 4-3 with a 2.81 ERA (26 ER/90.0 IP). In 2012, Greene was 8-4 with a 3.38 ERA (79 ER/198.0 IP) over 116 games between Double-A Trenton and Gwinnett. He led the South Atlantic League in wins and innings pitched and was named the circuit's MVP. Greene was drafted by the Padres out of high school in 2007. He missed most of 2008 due to injury but came back in 2009 to post a 10-5 record and 2.85 ERA in 26 starts between Class A Fort Wayne and Class A Lake Elsinore.