Mr. Briscoe became the first black starting quarterback in the NFL, at the time when it was believed that African-Americans couldn't lead a team on the field. Mr. Briscoe did what no one had done before. His performance on and off the field paved the way for future minority quarterbacks. As a rookie quarterback with the Denver Broncos, Mr. Briscoe set a NFL record by throwing 14 touchdown passes in 11 games. However, he never played quarterback again. After a visit to Canada, Marlin returned to the NFL where he was named All-Pro with the Buffalo Bills and won two Superbowl rings with the 1973-74 Miami Dolphins.
From the Marlin Briscoe football camp site.
Sounds successful to me.
But I sit corrected about him not ever being a starting QB, which he was (for one year).