Riley recorded 65 interceptions in his career, which was the fourth most in NFL history at the time of his retirement.

In 2023, several decades after his career ended, he was posthumously elected to the Pro Football Hall of Fame.

Under coach Jake Gaither, Riley led the Rattlers to a 23–7 record and three Southern Intercollegiate Athletic Conference titles.

After graduation, Riley also earned a Master's degree from the University of South Florida and occasionally worked as a substitute high school teacher during his NFL off-seasons.

When Riley reported to training camp, Cincinnati head coach Paul Brown decided to convert Riley to the cornerback position, as the team had selected quarterback Greg Cook with the 5th pick of the draft and he was expected to be their quarterback of the future.

Riley started his career with Cincinnati in its second and last year in the American Football League.

He made his first interception in his fifth game, doing so against the Denver Broncos off Pete Liske (throwing his only pass).

[8] In the playoff game that year, Riley recorded an interception off Ken Stabler, but the Bengals lost to the Oakland Raiders 31–28.

In 1976, he recorded a career high in interceptions, picking off nine passes while returning one for a score with two fumble recoveries.

Meanwhile, his defensive back teammate Lemar Parrish, who recorded just 2 interceptions and missed half the season with injuries, was a Pro Bowl selection.

He took one of them back for a touchdown to help levy the Bengals to a 31–17 win; it was the only game the Raiders lost in the regular season.

[14] After his playing career ended, Riley spent two years as an assistant coach for the Green Bay Packers.

In 2010, he was named as a part of the Pro Football Researchers Association "Hall of Very Good" class of 2010.

[16] Riley was posthumously inducted to the Bengals Ring of Honor as a part of their inaugural class.

On August 17, 2022, Riley was announced as one of the three finalists nominated by the senior committee for induction in the 2023 Pro Football Hall of Fame class along with Joe Klecko and Chuck Howley.

At the 2023 NFL Honors, he was announced being a member of the 2023 Hall of Fame class, becoming the second player who spent all of his career with the Bengals to be inducted and the fourth overall.