Complex sentence: In 2009, Jewett became a manager in the Nationals' minor league system, leading their High-A affiliate, the Potomac Nationals, in 2009, and receiving a promotion to manager of the Triple-A Syracuse Chiefs for 2010.
Split into simpler sentences: In 2009, Jewett began his first of two years as a manager in the Nationals' minor league system. He led their High-A affiliate, the Potomac Nationals, in 2009 before being promoted to manage the Triple-A Syracuse Chiefs for 2010.