Jelks began his professional managerial career in 2000 when he helped coach Australia at the 2000 Sydney Olympics and started head coaching in 2002 when he took the helm of the Evansville Otters of the independent Frontier League. In 2006, he was appointed to a coaching role for the national team at the 2006 World Baseball Classic.
Later that year, Greg led the Otters to a championship 2006. The following season, he was hired by the Frontier League as the manager of the fledgling expansion team the Slippery Rock Sliders. The Sliders were a concept team, building off a unique relationship with Slippery Rock University. Following a year of poor fan reception and a last place finish in the league, the Slippery Rock Sliders folded and the franchise became the Midwest Sliders, a travelling team in the league's Eastern Division. Greg Jelks was hired by the Washington Wild Things the following December, and began the 2008 season managing his third Frontier League franchise.[4] Jelks was let go by the Wild Things after he did not lead them to the playoffs, and to a 48–48 record.[5]
Death
On a flight en route to Australia from the United States, Jelks fell asleep and could not be woken up, later being pronounced dead on January 6, 2017, aged 55.[6] Jelks became the first (and only, as of 2024) MLB player in history to have died in Australia.[7]