Otis Armstrong, a Big Ten MVP, consensus All-American, and College Football Hall of Famer from Purdue, joined the Mile High City as the ninth overall pick in the first round of the 1973 draft. Initially serving mostly as a backup behind legendary Floyd Little and focusing on kick returns as a rookie, Armstrong dramatically elevated his performance in his second season once he became a full-time starter.

Armstrong's standout 1974 season was one of the most dynamic in the era. He topped the NFL in rushing with 1,407 yards, averaging an impressive 5.3 yards per carry. Additionally, he caught 38 passes for 405 yards, leading the league in yards from scrimmage with 1,812 and earning an Approximate Value of 21. His performance earned him Consensus First-Team All-Pro honors and his first Pro Bowl selection.

A serious injury sidelined nearly all of his 1975 season, allowing him only four games. Nevertheless, Armstrong made a strong comeback in 1976 with his second 1,000-yard season, rushing for 1,008 yards and earning his second Pro Bowl selection. His ability to contribute in multiple ways out of the backfield was vital for Red Miller's team as Denver entered its first successful period.

Although recurring leg and spinal injuries kept him from reaching those statistical heights again, Armstrong remained a vital part of the backfield rotation. He contributed to Denver's historic 1977 AFC Championship run and Super Bowl XII appearance, grinding out tough yards until retiring after the 1980 season.

Over his Denver run, Armstrong had 4,453 rushing yards, 25 rushing touchdowns, 131 receptions, 1,302 receiving yards, and 30 total touchdowns.