Randy Gradishar (1974-83)
Denver had high hopes when they picked the first-team All-American in the first round of the '74 draft, and Gradishar more than lived up to them. He became the starting middle line backer in his second season, then took over at RILB the following year when the team switched to the 3-4 defense. Over his career, Gradishar was chosen for seven Pro Bowls, and was a two-time All-Pro. His impressive numbers include 20 INTs (three TD returns), 13 fumble recoveries (two TDs), 20.5 unofficial sacks, and, most impressively, 2,049 tackles (unofficial, based on team records). That's an incredible average of over 200 tackles per season (including four 14-game seasons). Gradishar has been on the Hall of Fame ballot multiple times, but has yet to be voted in.
Tom Jackson (1973-86)
The slightly undersized (5'11', 220lbs.) Jackson was a skillful and determined player who was the heart of Denver's "Orange Crush" defense. He made three consecutive Pro Bowls ('77-'79) and was an All-Pro pick following the 1977 Super Bowl season. The well-rounded Jackson amassed 20 INTs (three TD returns), 44 (unofficial) sacks, and eight fumble recoveries, and he annually ranked among the team's tackling leaders. He was voted to the Ring of Fame in 1992.
Karl Mecklenburg (1983-94)
The talented Mecklenburg settled into the starting RILB position in his third year, occasionally seeing spot duty at defensive end. His strength and agility allowed him to maneuver around blockers to pressure the QB or put the wraps on ball carriers. In 180 games with Denver, he accumulated 79 sacks, 14 fumble recoveries (two TD returns), and over 1,100 tackles. His efforts garnered him six Pro Bowl berths, three All-Pro selections, and a 2001 Ring of Fame induction.
Simon Fletcher (1985-95)
It was difficult to leave the team's all-time sack leader (with 97.5) off of the starting list, but Fletcher was not as well-rounded as the players mentioned above. He was far from being one-dimensional though, as his 800+ tackles and 10 career fumble recoveries would indicate. Never made a Pro Bowl, despite being the only player in team history to record double-digit sacks for five consecutive seasons ('89-93). He actually set an NFL record by registering a sack in 10 straight regular season games (between the '92 and '93 seasons).
Al Wilson (1999-2006).
One of the faster linebackers in the game, Wilson used his quickness to both sniff out running plays before they got started and to shut down TEs in passing situations. Sadly, he suffered a neck injury late in the 2006 season and was released the following year due to salary-cap issues. He officially retired prior to the 2008 season, but left his Bronco legacy by earning five Pro Bowl invitations and an All-Pro pick in 2005.
Bob Swenson (1975-83)
Teamed with Gradishar, Tom Jackson, and Joe Rizzo during the late '70s to form one of the better linebacker units in NFL history. Swenson, the LOLB, was on the verge of coming into his own when an injury sidelined him for the entire 1980 season. He returned with a stellar effort in '81, making the Pro Bowl and receiving All-Pro status. Unfortunately, injuries continued to hamper him, and he saw action in only six games during his final two seasons.
John Mobley (1996-2003)
Like Bob Swenson, Mobley's promising career was cut short by recurring injuries. He immediately assumed the starting right linebacker role his rookie year, and made All-Pro the following year, helping Denver to its first Super Bowl win. He missed most of the '99 campaign due to injury, but returned to his starting position the following year. The end came in 2003 when he suffered a midseason spinal-column injury, which eventually forced him into retirement. For his career, he made over 600 tackles, 10.5 sacks, and returned one of his five career INTs for a touchdown.
Jim Ryan (1979-88)
After spending his first three seasons as a backup, Ryan took over the LOLB position in '82 after injuries got the better of Bob Swenson. Ryan did not disappoint, and he remained a starter through the close of his career. He never received postseason honors, as his steady play often went unnoticed amid Denver's star-studded defenses of the '80s. Bronco fans won't soon forget Ryan's key INT during the legendary '86 AFC Championship game.
Bill Romanowski (1996-2001)
Although he wasn't the most respected or well-liked player in the league, Romanowski was a fierce competitor who provided the Broncos with the attitude and intensity that guided them to two Super Bowl championships. In his six seasons, he never missed a game or starting opportunity: compiling 23 sacks, 11 INTs (one TD), and over 400 tackles. He made the Pro Bowl in '96 and '98.