Duane Thomas, a former NFL running back and one of the key players on the Dallas Cowboys’ first Super Bowl championship team, has died at age 77, team officials have told The Dallas Morning News.

Thomas’ NFL career is largely remembered for two things: his role in the Cowboys’ first championship and his enigmatic behavior that season that eventually led to his short tenure with the franchise.

Thomas was coming off one of the best rookie seasons in NFL history entering the 1971 offseason. He had helped the Cowboys reach their first Super Bowl on the strength of his league-best 5.3 yards-per-carry average (which stood as the best single-season mark in franchise history until Emmitt Smith matched it in 1993). Thomas wanted a bump in pay entering the 1971 season, but the Cowboys didn’t budge, leading to Thomas being traded to New England.

Things went so badly for Thomas in New England that NFL commissioner Pete Rozelle actually nixed the deal shortly after it had been made. Upon his return to Dallas, Thomas refused to speak to anyone — including teammates and coaches — throughout the entire season, and would only respond to people with mumbles or grunts, according to teammates.

“I didn’t come in with an attitude of disruption,” Thomas once said in a documentary on the ’71 Cowboys. “However, when I exposed my true personality, it was disruptive to other personalities on the team. But it was not disruptive to the performance of the team.”

While remaining silent, Thomas continued to make noise on the field in 1971. That season, he led the NFL in rushing touchdowns while helping the Cowboys win a sixth consecutive division title. Thomas scored three touchdowns in Dallas’ three playoff games that included a 3-yard scoring run against the Dolphins in Super Bowl VI.

That day, Thomas ripped through the Dolphins’ “No Name” defense to the tune of 95 yards on 19 carries. He also caught three passes as the Cowboys posted a 24-3 victory.

“It’s a sense of accomplishment that … like I haven’t had anything to replace it yet,” Thomas said of the win nearly 35 years later.

As memorable as Thomas’ performance was, his postgame interview was equally notable. With Hall of Fame running back Jim Brown standing beside him, Thomas was asked by CBS Sports’ Tom Brookshier if he was actually as fast and quick as he appeared to be that day.

“Evidently,” Thomas said, which quickly led to laughter from everyone in the champions’ locker room.

Ironically, Brown was the running back Thomas’ teammate and Hall of Fame defensive tackle Bob Lilly said that Thomas reminded him of. That was certainly high praise, as Brown is widely regarded as arguably the greatest football player of all time. Like Brown, Thomas possessed a blend of patience, quickness and power that made him extremely difficult to stop.

“Duane Thomas gave everything he had,” Cowboys Hall of Fame quarterback Roger Staubach said of Thomas. “He blocked hard, he ran hard, he played hard, and he was very smart. Duane rarely made a mistake.”

Unfortunately for Thomas, the thing that ultimately stopped him from achieving more success with the Cowboys was his resentment toward the team over his contract. The team ultimately parted ways with him before the start of the 1972 season. Thomas didn’t play at all during the 1972 season before finishing his career with two largely quiet seasons with Washington.

While his career was short and tumultuous, Thomas’ legacy as it relates to his impact on the Cowboys’ first championship remains in tact. His talent is also something that continues to be remembered by those who witnessed it.

“I just can’t tell people enough how good he was,”  Lilly once said of Thomas. “I just had visions of Jim Brown coming back to life. Duane, he had those same moves, the ones where you think you have him, and he wiggles out of it or he gives you a limp leg.

“He could really go off-tackle, about as good as I ever saw, and start needing his way through the linebackers and the secondary. Almost like music. In fact, I can see it right now.”