Armstead was a shining star for the 49ers in 2019. The 26-year-old had nine sacks in his first four seasons combined but exploded with 10 for the NFC West champions. He was part of a dominant defensive line that also featured Nick Bosa, DeForest Buckner and Dee Ford.
In addition to his career-high sack total, Armstead set personal bests with 54 combined tackles, 18 quarterback hits and 11 tackles for loss. His breakout performance was one of the biggest reasons San Francisco's defense went from 28th in points allowed in 2018 (435) to eighth in 2019 (310).
The 49ers found themselves in a cap crunch this offseason with only $9.9 million available, per Over the Cap.
Based on Armstrong's performance and the salary he could command on the open market, San Francisco could have let him test the free-agent waters. Rather than risk breaking up one of the most integral parts of the team's surprise success, though, the 49ers carved out enough cap space to retain their young star.
Given his age and development, Armstrong is trending upward and can establish himself as one of the league's best pass-rushers with another dominant performance in 2020.