Jim Riley, a defensive end out of Oklahoma University, was drafted by the Dolphins in the second round, 29th overall, of the 1967 draft.
He made the sophomore Dolphin's squad, still part of the American Football League, out of training camp, appearing in all 14 games at whatever defensive line position he was needed off the bench.
In 1968, Riley appeared in 13 games, starting nine at the left defensive end position. After losing the first three games by a combined 85 points, the Dolphins defense stiffened up, limiting the Houston Oilers to 86 rushing yards and collecting seven turnovers in a 24-7 Dolphins victory. They would compile a respectable 4-5-1 record for the rest of the season.
In 1969, Riley assumed the starting spot at left defensive end for the whole season, starting all 14 games. The Dolphins were again unimpressive, winning only three games that year.
1970 would see the Dolphins join the NFL under a new coach, the legend Don Shula. Although they lost their first playoff game to the Oakland Raiders, 21-16, Shula led the team to their first winning record, finishing 10-4. Riley started all 15 games. During one four game stretch in the middle of the season, the Dolphins allowed only 251 rushing yards and stole 13 possessions from the opposition.
Miami would win the AFC title in 1971 with a team best 12-3-1 record (including the playoffs). They would be famously blown out of Super Bowl VI by the Dallas Cowboys, 24-3. Riley started 13 regular season games, and made his last career NFL appearance in the Super Bowl, retiring after the season at the age of 26.
Altogether, Riley played 68 games for Miami over his five seasons, starting 50 as the Dolphins left defensive end.