He caught 378 passes and scored 52 touchdowns during his career, which began with the Raiders in Oakland in 1974 and included stints with the Oilers and Minnesota Vikings before concluding with the Raiders in Los Angeles in 1984. He was selected to play in five Pro Bowls, and was named All-Pro and All-AFC four consecutive years.

Casper was also involved in "The Holy Roller", one NFL history's strangest plays. The Raiders were trailing the San Diego Chargers with 10 seconds remaining. Quarterback Ken Stabler fumbled the ball forward 13 yards before running back Pete Banaszak swatted it toward the end zone. The ball glanced off Casper's foot at the five yard line and he chased it into the the end zone, falling on it for the game-winning touchdown.

A new rule was spawned by the play, making it illegal to advance the ball in such a manner.

Career Highlights
1970s All-Decade Team
Super Bowl Silver Anniversary Team
All-Pro: 1976 (AP, PFWA, NEA, PW), 1977 (AP, PFWA, NEA, PW), 1978 (AP, PFWA, NEA, PW), 1979 (AP, PW)
All-Pro Second Team: 1979 (NEA)
All-AFC: 1976 (AP, UPI, SN, PW), 1977 (UPI, SN, PW), 1978 (UPI, SN, PW), 1979 (PW)
Pro Bowls: 1977, 1978, 1979, 1980, 1981
Inducted into the Pro Football Hall of Fame in 2002

Championship Teams
1976 AFC Champions - Oakland Raiders

Super Bowl Teams
Super Bowl XI - Oakland Raiders 32, Minnesota Vikings 14