NEW YORK - Gene Upshaw was a punishing blocker who intimidated opponents on the field. Off it, his power was greater.

A Hall of Fame guard for the Oakland Raiders, Upshaw died Wednesday at age 63 from pancreatic cancer, an illness he only learned about Sunday. His death cut short a 25-year, post-playing career as union boss in which he led NFL players to riches that would have been almost unimaginable when he was a rookie in 1967.

“The Raider organization, the National Football League, and the world have lost a great man,” Raiders founder Al Davis said. “He is as prominent a sportsman as the world has known.”

The unexpected nature of Upshaw's death shocked people throughout the NFL. This was a towering man who played 15 years - all for an Oakland team that reached the Super Bowl three times and won twice.

Upshaw died Wednesday night at his home near California's Lake Tahoe, the NFL Players Association said Thursday. His wife Terri and sons Eugene Jr., Justin and Daniel were by his side. NFLPA president and Tennessee Titans center Kevin Mawae said Upshaw was diagnosed Sunday after he fell ill and his wife took him to the hospital.

“Gene was a great player. He was an All-Pro. He was a Hall of Famer. If you look at the history of the NFL you're going to find out that he was one of the most influential people that the league has known. He did so much, not only for the players, but also for the owners, the teams, and the game of pro football,” John Madden, who coached Upshaw when Oakland won its first Super Bowl, said in a statement.

“This is deeper than head of the union passing away, and it's deeper than an ex-player. This is missing someone that is and was like family. It's a tough day for all of us.”

In the wake of his death, many of those who had made him the focal point for their complaints over pension and health benefits for retired players softened the rhetoric and spoke of their respect for Upshaw.

As a player, the seven-time Pro Bowler was one of the best ever, elected to the Hall of Fame in 1987, the first time he was eligible.

That also was the year Upshaw led the second players' strike in five years, a short walkout that led to the embarrassing spectacle of games with replacement players, or “scab football” as it was jokingly called at the time.

By 1989, while the union was