DAYTONA BEACH, Fla. (AP) - NASCAR is replacing longtime Sprint Cup Series director John Darby with Richard Buck. The move comes four years after NASCAR first announced it was seeking a successor to Darby so he could take a managerial role. Buck spent last year as vice president of racing operations for the International Motor Sports Association and managing director of NASCAR's Touring Series. He worked from 1980 to 2000 as a crew chief, team manager and director of operations with Champ Car teams, and won five Indianapolis 500s as a crew chief. He worked with teams in all three NASCAR national series before joining NASCAR in 2005. Darby was named Sprint Cup director in 2002. A no-nonsense official, he oversaw the implementation of the "Car of Tomorrow" in 2007 and the "Gen-6" car last season.