[4][5] He attended Omaha South High School,[2][4] where he starred in several sports and played at running back for a football team that won the state championship.

[7] Briscoe was 5 ft 10 in (1.78 m) and 177 pounds (80 kg) when the AFL's Denver Broncos selected him in the fourteenth round of the 1968 draft at age 22.

[8] On September 29, 1968, starter Steve Tensi suffered a broken collarbone, and backup Joe DiVito was spotty.

Head coach Lou Saban summoned Briscoe from the sidelines in the fourth quarter against the Boston Patriots to give him a try.

[12] He threw 14 touchdown passes that year in just five starts, including four on November 24 against Buffalo; both are still Broncos rookie records.

[8] Before the 1969 season started, Briscoe, still determined to play quarterback, discovered that head coach Saban intended to use Pete Liske as the starter, so he asked to be released.

In 1971, the Bills traded him to the Miami Dolphins for the first-round draft pick used to take Joe Delamielleure, who developed as a Hall of Fame guard.

Briscoe led the undefeated 1972 team with four touchdown receptions and was the leading receiver on the Dolphins in 1973,[14] catching more passes than future Pro Football Hall of Famer, Paul Warfield.

[17] He was one of the fifteen plaintiffs in Mackey v. National Football League in which Judge Earl R. Larson declared that the Rozelle rule was a violation of antitrust laws on December 30, 1975.