Keith Sims was a 6'3", 318 pound guard out of Iowa State University, and was later elected into the Iowa State Hall of Fame. Miami selected him with their second round pick of the 1990 NFL Entry Draft with the 39th overall pick after choosing offensive tackle Richmond Webb with their first round pick. The two were a formidable pair for several years on the left side of Miami's offensive line.
Next to Webb, Sims started 13 of 14 games his rookie season of 1990. The Dolphins posted a 12-4 record, earning a wildcard berth in the postseason. After defeating the Kansas City Chiefs 17-16, they dropped the divisional round at the Buffalo Bills 44-34. The Dolphins offensive line allowed an NFL low 16 sacks through the season.
Dan Marino passed for nearly 4,000 yards in 1991 as Miami posted an 8-8 record, missing the playoffs. Sims missed four games in the middle of the season due to injury, but started the other 12 at left guard.
In 1992, Sims started every game at left guard. Miami returned to the playoffs, winning the AFC East with an 11-5 record and defeating the San Diego Chargers 31-0 in the Divisional Round before losing to the Bills, 29-10 in what was becoming a recurring theme. The offensive line allowed an AFC low 28 sacks of quarterback Dan Marino, while allowing him to rack up an NFL second best 3,975 passing yards.
1993 would see Sims retain his starting position, again starting every game while earning his first Pro Bowl selection. Miami missed the playoffs with a 9-7 record, but led the AFC with 5,812 total yards of offense and 5.6 yards per play, also leading the NFL with 4,353 passing yards.
In 1994, Sims started all 16 games at left guard, earning his second consecutive Pro Bowl selection while also earning a spot on the UPI All-AFC first team and the AP All-NFL second team. Miami qualified for the playoffs with a 10-6 record, beating the Chiefs 27-17 in the wild card round before letting the Chargers squeak by, 22-21 in the Divisonal Round. Miami led the NFL with 6,078 total offensive yards while allowing only 18 sacks, second only to the Cleveland Browns 14.
Sims again started every game at left guard in 1995, earning his third consecutive Pro Bowl start and second team UPI All-AFC honors. Miami posted a 9-7 record, losing to the Bills 37-22 in the AFC Wildcard game. The offensive line again ranked in the NFL top ten by allowing only 29 sacks to opposing defenses.
Sims started 19 of Miami's next 23 games at left guard before joining the Washington Redskins in 1998. In eight seasons with the Dolphins he started 108 of 113 games at left guard.