Upon leaving high school, Jeong was considered the top infielder prospect for the 2001 KBO Draft, but went undrafted. Instead, he played college baseball at Korea University.
In November 2003, Jeong competed for the South Korean national team as an amateur player again in the 2003 Baseball World Cup. In the tournament, he batted .308 with 2 home runs and 10 RBIs, leading the team in RBI. In Team Korea's second game against Russia, he went 5-for-6 with a home run and 5 RBIs to lead his team to a 26-3 victory.
Drafted by the SK Wyverns in the second round (15th overall) of the 2005 KBO Draft, Jeong made his pro league debut on April 2, 2005. He had a disappointing rookie season, managing only a .193 batting average.
In the 2008 KBO season, Jeong hit .300-plus once again (.317), and ranked 2nd in hits (154) and 3rd in stolen bases (40).
On July 16, 2008, Jeong was selected for South Korea national team in the 2008 Olympics. In Beijing, he batted 9-for-29 with 4 runs and a RBI, playing as a utility infielder. In the team's third game of round-robin play against Canada, he smacked a solo home run off Mike Johnson in the third inning that held up for a 1-0 win for South Korea.
On December 11, 2009, he obtained his second Golden Glove Award as a second baseman,[2] and in 2013 he won his third Golden Glove.
He moved through the second draft of the KBO League in 2020.[3]
^Baek Seung-hoon (October 21, 2021). "피의 게임' 전 야구선수 정근우→한의사 최연승, 플레이어 공개" [Game of Blood' former baseball player Jeong Geun-woo → Oriental doctor Yeon-seung Choi, player revealed] (in Korean). iMBC. Retrieved October 21, 2021 – via Naver.
^Moon Ji-yeon (February 15, 2022). "올 탁구나!' 이진호·강승윤·신예찬·이태환, 멤버 완성..포스터 공개" ['All table tennis!' Lee Jin-ho, Kang Seung-yoon, Shin Ye-chan, Lee Tae-hwan, members completed.. Poster released] (in Korean). Sports Chosun. Retrieved February 15, 2022 – via Naver.
^Park Ah-reum (April 13, 2022). "청춘야구단' 정수성 작전코치 합류 "프로선수 수준으로 지도할 것" [Joining ‘Youth Baseball Team’ as operational coach Suseong Jung “I will guide you to the level of a professional player”] (in Korean). Newsen. Retrieved April 13, 2022 – via Naver.
^Kang Ae-ran (April 21, 2022). "이승엽·박용택 등 레전드 총출동…예능 '최강야구' 상반기 방송" [Lee Seung-yeop, Park Yong-taek, etc. Legends all dispatched… 'Strongest Baseball' broadcast in the first half of the entertainment show] (in Korean). Yonhap News. Retrieved April 21, 2022 – via Naver.
