 In 2007, Mock posted a win-loss record of 2–7 and an ERA of 5.12 in 15 appearances for the High Single-A Potomac Nationals, Rookie-Level Gulf Coast Nationals and Double-A Harrisburg Senators.During the 2007–2008 off-season, Mock pitched for the Peoria Javelinas of the Arizona Fall League.On October 23, 2007, Mock was added to the Nationals 40-man roster.