Seau starred at USC, wearing jersey No. 55, which is given to linebackers ready for the next level. Seau, an All-American in his junior season, decided to forgo his final season of eligibility and enter the NFL Draft. Seau was taken No. 5 overall in 1990 by the San Diego Chargers.

Seau became an immediate sensation in San Diego and started all but one game during his rookie season. He logged 85 tackles and was named to the 1991 Pro Bowl as an alternate.

Seau played 13 seasons for the Chargers and played in 12 consecutive Pro Bowls. Seau had a career year in 1994, racking up 155 tackles and helped his team to an appearance in Super Bowl XXIX. He was also named an All-Pro 10 times during his stay in San Diego.

Seau was instrumental in the Chargers’ only Super Bowl berth in the 1994 season, as he had 19 tackles in the AFC Championship Game against the Pittsburgh Steelers. The Chargers' run fell short in the Super Bowl, when the 49ers' Steve Young-led attack hung 49 points and eventually hoisted the Lombardi Trophy.

After spending 12 years in San Diego, Seau was traded to the Dolphins in 2003. He started 15 games in his first season, compiling 96 tackles with three sacks. Injuries derailed his next two campaigns in Miami and he was finally released in 2006.

Seau's career appeared to be over when he signed a one-day deal with the Chargers and announced his retirement during a news conference on Aug. 14, 2006. However, that retirement lasted just four days as the Patriots came calling with a contract. The highlight of his four seasons in New England was being named one of the team's captains in 2007 and playing in Super Bowl XLII against the New York Giants.

Seau left the Patriots following the 2009 season. Despite not having officially declared his retirement, Seau was inducted into the Chargers' Hall of Fame in 2011. He also did various television and charity work.

Seau was hospitalized in 2010, when the SUV he was driving plunged off a seaside cliff. Seau said he had fallen asleep while driving and suffered minor injuries in the incident.