Clay Matthews Jr. carried on an unmatched football lineage. The son of four-year NFL veteran Clay Matthews Sr. and older brother to Pro Football Hall of Fame offensive lineman Bruce Matthews, Clay Jr. spent the first 16 of his 19 professional seasons in Cleveland after he was drafted 12th overall in 1978. He established himself as the ultimate defensive iron-man and a quintessential franchise leader, anchoring the Browns' linebacker corps throughout the late 1970s, 1980s, and early 1990s.

Matthews combined instincts, tactical reading of backfield flows, and rare physical durability. Operating as an outside linebacker in both 4-3 and 3-4 schemes, he possessed the lateral quickness to scrap over the top of blocks to shut down perimeter runs, while also boasting the bend and power to drop quarterbacks off the edge. His longevity and ability to play every down made him the emotional heartbeat of Marty Schottenheimer's physical defenses.

Matthews took over as a full-time starter in his second season in 1979. Over his 16-year run in Northeast Ohio, he recorded eight seasons with at least 100 tackles and led the NFL in combined tackles four times. He hit his pass-rushing stride in 1984, logging a career-high 12.0 sacks and earning Second-Team All-Pro honors.

His peak prime coincided with Cleveland's late-1980s surge, earning four Pro Bowl selections in a five-year span (1985, 1987–1989). Matthews was on the field for the franchise's most iconic AFC Championship battles. His signature postseason moment arrived in the 1989 AFC Divisional Playoff against Buffalo, when he intercepted Jim Kelly at the 1-yard line with seconds remaining to seal a 34–30 victory and propel Cleveland to the AFC title game.

Matthews departed Cleveland following the 1993 season, joining the Atlanta Falcons for three final years before retiring at age 40 as the oldest player in NFL history to record a sack (40 years, 282 days). Across his 232 regular-season games with the Browns, he accumulated 1,430 tackles, 62.0 sacks, 14 interceptions, and 24 forced fumbles. In 2019, Cleveland officially recognized his case for Canton by inducting him into the Cleveland Browns Ring of Honor.