One of the athletic feats for which Youngblood is best known, is that of playing the entire 1979 playoffs, including Super Bowl XIV, with a fractured left fibula. He also played in the 1980 Pro Bowl with the injured leg, a week after the Super Bowl. In the playoffs, Youngblood sacked Dallas Cowboys quarterback Roger Staubach near the sideline in the waning moments of the divisional playoff game versus the Cowboys. Playing with the fractured leg was noted by Sports Illustrated in their Top 10 list of athletes playing in pain. For that and other achievements Jack was dubbed the “John Wayne of football” by Jim Hanifan and echoed by Hall of Fame coach John Madden. The NFL Network series NFL Top 10 selected Youngblood's performance in the 1979 playoffs as top on its list of the “Gutsiest Performances″ of all-time.
For the 1979 season Youngblood had a career-high 18 sacks and was a consensus First-team All-pro for the fifth time. He was voted to his seventh consecutive Pro Bowl. In 1980 he was Second-team All-pro and First-team All-NFC while leading the Rams with 11½ sacks. In 1981 Jack led the Rams with 12½ sacks and was the Rams outstanding defensive lineman. In the off-season, prior to the 1981 season, Jack had emergency surgery to remove a hot-dog sized blood clot from under his left arm. It was a result of repeated trauma to a nerve in his arm that blocked the flow of blood. Despite the broken leg and numerous other injuries, Youngblood played in 201 consecutive games, a Rams team record; and only missed 1 game in his 14-year NFL career. He played in seven straight Pro Bowls, 5 NFC Championships, and one Super Bowl. He was also the Rams defensive captain from 1977 through 1984 and was voted the Dan Reeves award 3 times, which is awarded to the team's MVP. He had 151½ career sacks and led the Rams in sacks nine times despite playing first in assistant Coach Ray Malavasi's stop-the-run-first defensive scheme and then in his final two seasons in Defensive Coordinator Fritz Shurmur's 3-4 two-gap scheme which limited some pass rush opportunities to make sure the opponent's running game was handled.