Glenn Blackwood was a 6' defensive back for the University of Texas Longhorns. Miami chose him in the eighth round of the 1979 NFL Entry Draft with the 215th overall pick.
As a rookie in 1979, Blackwood made 20 tackles over 11 games in relief of Tim Foley at strong safety. Miami benefitted from the return of Larry Csonka (late of the Memphis WFL franchise and the New York Giants) to post a 10-6 record, making the playoffs. The Pittsburgh Steelers knocked Miami out in the first round, 34-14.
In 1980, Blackwood assumed a starting role with the team, getting 15 starts at strong safety while appearing in every game. He started out the season by twice intercepting Bills quarterback Joe Ferguson in a 17-7 Miami victory. He finished the year with around 95 tackles and three interceptions with 10 passes defensed and two fumble recoveries as Miami finished 8-8.
1981 would see Blackwood start out strong, picking off three passes in the first two games of the season, finishing with a total of four on the year. The team finished out 11-4-1, winning the AFC East before bowing out in the Epic in Miami to the San Diego Chargers, 41-38 in overtime. Blackwood, teamed with his older brother Lyle in the defensive secondary for the first time, finished with around 80 tackles while starting all 16 games.
In 1982, the season was marred by the players strike to nine regular season games. Miami finished 7-2, getting to Super Bowl XVII and losing to the Washington Redskins, 27-17. The season was marked by the emergence of the "Killer B's" as several players on the starting defense had last names beginning with the letter B. In addition, Glenn and his brother Lyle earned the additional moniker, the "Bruise Brothers." Glenn started every game, finishing the season with two interceptions, returning one 35 yards for his only career touchdown in a week one 45-28 victory over the New York Jets. He also helped avenge the prior seasons loss in the playoffs by twice intercepting San Diego quarterback Dan Fouts in the AFC Divisional playoff, en route to a 34-13 victory.
Glenn would start every game in 1983 and 1984, collecting nine interceptions over the two seasons. Miami finished 12-4 in 1983, losing in the first round of the playoffs before coming back in 1984 with a 14-2 record and a berth in Super Bowl XIX. Miami lost to maybe the only team that could have beat them, the San Francisco 49ers, 38-16.
Glenn collected an NFL tenth best and team leading six interceptions in 1985 for the second year in a row while starting 14 games. The team missed out on their third Super Bowl in four seasons by losing the AFC Championship to the New England Patriots, 31-14 after posting a 12-4 record in the regular season.
Blackwood started 20 more games over the next two seasons, making five more interceptions. He concluded his NFL and Miami Dolphins career after starting 106 of 118 games, all at strong safety, and is fourth on Miami's all-time leaderboard with 29 interceptions and with 14 fumble recoveries (not counting Dan Marino and Bob Griese's fumble recoveries).