Dalby was a star linemen at center and defensive end, who led his high school football team, the La Serna Lancers, of Whittier, California, to the California Scholastic Federation AAA Football Championship in 1967. An All Around athlete in high school, Dalby also played basketball and baseball at La Serna High School.
He replaced Hall-of-Famer Jim Otto as the starting center when the latter retired after the 1974 season, becoming only the second starting center in franchise history; Otto had been the starter since the team's inception in 1960. For the next decade, Dalby was a part of sterling offensive lines which culminated in 3 Raider Super Bowl victories: Super Bowl XI, Super Bowl XV, and Super Bowl XVIII. During that 1975-1985 window, the Raiders reached the playoffs 8 times (1975 to 1977, 1980, 1982 to 1985). Dalby played in that 1975 to 1985 span next to Hall-of-Famer Gene Upshaw, Curt Marsh, and Charley Hannah at left guard with George Buehler and Mickey Marvin at right guard. He was selected to the Pro Bowl once, after the 1977 season. After his retirement, he was replaced as the starting center in 1986 by Don Mosebar.