MIAMI (AP) — Pro Football Hall of Fame middle linebacker Nick Buoniconti, an undersized overachiever who helped lead the Miami Dolphins to the NFL’s only perfect season and became a leader in the effort to cure paralysis, has died at the age of 78.

Buoniconti died Tuesday in Bridgehampton, New York, said Bruce Bobbins, a family spokesman.

In recent years, Buoniconti struggled with symptoms of CTE, a degenerative brain disease associated with repeated blows to the head. He had recently battled pneumonia, Dolphins senior vice president Nat Moore said.

The 5-11, 220-pound Buoniconti was bypassed in the NFL draft but went on to a 15-year career. He was captain of the Dolphins’ back-to-back Super Bowl champions, including the 1972 team that finished 17-0.

Following retirement, Buoniconti and his son, Marc, worked to raise more than a half-billion dollars for paralysis research. The younger Buoniconti was paralyzed from the shoulders down making a tackle for The Citadel in 1985.

Marc Buoniconti said his father was his biggest hero.

“He could have been sitting on the beach sipping champagne for the rest of his life,” the younger Buoniconti said in 2017. “But what did he do? He went around and gave the rest of his life to help his son.”

Following retirement, Buoniconti worked as an attorney, a broadcaster, as president of U.S. Tobacco and as an agent to such athletes as Bucky Dent and Andre Dawson. For 23 seasons he was co-host of the weekly sports show “Inside the NFL” on the HBO cable network.

“He lived a life of honor and nobility, and his legacy will live forever through his Bronzed Bust in Canton, Ohio,” said Pro Football Hall of Fame president and CEO David Baker.

Buoniconti was chosen for the all-time AFL team in 1970, and for the NFL Pro Bowl in 1972 and 1973.

A native of Springfield, Massachusetts, Buoniconti played guard on offense and linebacker on defense for Notre Dame. He was small for a pro linebacker, but after being taken in the 13th round by the Boston Patriots of the upstart AFL, he played for them from 1962 to 1968.

He made the AFL All-Star Game six times and had 24 career interceptions for the Patriots, including three in a single game in 1968.

Buoniconti played for the Dolphins from 1969 to 1974 and in 1976. He was the leader of Miami’s famed “No-Name Defense” and in 1973 he set a team record with 162 tackles. He was inducted into the Hall of Fame in 2001.

In 1985, he and Marc Buoniconti helped to found the Miami Project to Cure Paralysis, which has become the world’s largest spinal cord injury research center.

“Marc, the Miami Project Team and I are committed to carry Nick’s banner and legacy forward to the goal line,” project chairman Dr. Barth Green said.