Christensen, 57, was scheduled to undergo a liver transplant on Tuesday, The Sports Xchange learned.
He battled liver disease and other ailments during the past few years, according to The Salt Lake Tribune. But he was known as an active and effusive person who kept himself in good shape. The health issue related to the surgery arose quickly.
Drafted by the Dallas Cowboys in the second round in 1978 out of Brigham Young, Christensen played 11 seasons in the NFL. He joined the Oakland Raiders in 1979 and won two Super Bowls (1980, 1983). Christensen was named to the Pro Bowl five times and twice was an All-Pro selection.
Christensen's best seasons came during the 1980s. He had 349 receptions from 1983 to 1986 and led the league in 1983 with 92 catches for 1,247 yards and 12 touchdowns. In 1986, he led the NFL in receptions again with 95.
After retiring as a player in 1988, Christensen became a television analyst for NBC and later worked as a host for American Gladiators and also as a football analyst for ESPN, the Mountain West Sports Network and CBS Sports Network.
In college at BYU, Christensen was a running back who had 152 receptions for 1,568 yards and 15 touchdowns from 1974 to 1977. He was inducted into the school's Athletics Hall of Fame in 1992.
Christensen began his NFL career with the Cowboys as a fullback but missed his rookie season after suffering a broken foot. He resisted when the Cowboys wanted to switch him to tight end during his second year and he was cut. He was picked up and released by the New York Giants before landing with the Raiders, who persuaded him to move to tight end.