Fennig continued to work with then-team owner Bobby Allison until Fennig left the team in October 1996 to join Roush Racing to become Martin's crew chief. Martin/Fennig had 4 wins in 1997, 24 Top 10s, and 3 poles to finish third in the points. Martin finished second in 1998 points with seven victories. They remained together for three more wins, until they went winless in the 2001 Cup season. Jack Roush moved Fennig to the No. 97 crew to be the crew chief for young Kurt Busch in 2002, and Ben Leslie became the crew chief for Mark Martin. The swap was a success as Busch won the NASCAR Nextel Cup Series title in 2004. It was the first year of the Chase for the Cup. Busch dedicated his title to Fennig. Fennig was named the Sporting News crew chief of the year. He continued in that role until 2006. He started out the season as Jamie McMurray's crew chief, and he became the head of Roush Racing Busch Series effort. Fennig became the crew chief for David Ragan after Ragan replaced Martin in the #6 car in 2007, and he remained in that role for 2008.
