In 2007, his sophomore year of high school, he help his team advance into the semifinals at the 59th Hwarang Flag National High School Baseball Championship, racking up two wins as a starting pitcher.
In 2008, Jung was selected for the South Korea national junior baseball team to compete at the 2008 World Junior Baseball Championship, where they claimed their fifth tournament title. He was named to the All-Tournament team alongside fellow hitter Oh Ji-hwan, batting .423 (11-for-26) with 2 RBIs and 4 runs in 9 games as the starting center fielder of the team.
Drafted by the Doosan Bears in the second round (39th pick, 47th overall) of the 2009KBO Draft, Jung became the youngest position player in franchise history to be named to the Bears' Opening Day 26-man roster since Jung Soo-Keun in the 1995 season. He made his pro league debut on April 5, 2009, as a pinch runner against the Kia Tigers. On April 22, Jung hit a game-winning two-run home run, which was his first professional home run, against the SK Wyverns in the top of the 12th inning. He finished his rookie season with a respectable .264 batting average, 3 home runs, 17 RBI and 13 stolen bases in 85 games.