A version of this story originally ran in February 2017.

ST. LOUIS -- There's likely no one in Cardinals history with a legacy more complex than Curt Flood, who sacrificed his standout career for a greater good from which he never personally benefited.

Flood remains one of the finest center fielders in franchise history. He joined the organization in 1958, won seven consecutive Gold Glove Awards beginning in '63 and hit better than .300 in six of his 12 years with St. Louis. Flood was also a key contributor on the Cardinals' 1964 and '67 World Series championship clubs.

However, who he was as a player will forever be overshadowed by what he meant to those who came after him. It was Flood who, upon being traded to the Phillies on Oct. 7, 1969, took a stand that would effectively end his career and change the sport forever.

Flood refused to accept the trade, and two months later he penned a letter to Commissioner Bowie Kuhn in which Flood began his fight against the reserve clause. This clause bound a player to one team unless that club chose to trade or release that player. There was no such thing as free agency then, and a 1921 Supreme Court case had ruled that baseball was exempt from antitrust laws.

With the backing of union chief Marvin Miller, Flood decided to challenge this system.

"After 12 years in the Major Leagues, I do not feel I am a piece of property to be bought and sold irrespective of my wishes," Flood wrote to Kuhn. "I believe that any system which produces that result violates my basic rights as a citizen, and is inconsistent with the laws of the United States and of the several States."

After Kuhn refused to grant Flood free agency, Flood filed a lawsuit against the Commissioner and MLB, alleging a violation of antitrust laws.

"Any time there is a major change in the game, it doesn't happen, for the most part, with a no-name player," said Brian Finch, a member of the Cardinals' museum staff for 17 years and connoisseur of franchise history. "For all that Jackie Robinson went through, he had to be able to show on the field what he could be for them to put up with all that happened off the field. It was the same with Curt Flood. Owners weren't going to listen to someone that they knew was disposable. Flood was an outstanding, All-Star, Gold Glove center fielder. You can't replace those."

Nevertheless, Flood understood that his fight would also derail his career. After sitting out the 1970 season, Flood, at 33 years old, appeared in 13 games in '71 for the Washington Senators. That marked the end of his on-field career.

In 1972, Flood's case against MLB reached the Supreme Court, which ruled, 5-3, in favor of MLB. No active players stepped out to testify -- or even attend -- the trial in support of Flood.

However, the lost case wasn't a lost cause. In 1976, pitchers Andy Messersmith and Dave McNally agreed to play without contracts, and they were later ruled free agents by arbitrator Peter Seitz. The reserve clause disintegrated, and the groundwork for free agency as we know it today was laid.

"The fact that Curt Flood, one of the best all-around players of his generation, was willing to risk it all for others is one of the greatest displays of personal sacrifice known to the sports world," said Tony Clark, the executive director of the MLB Players Association.

"It takes years of dedication and perseverance to make it to the Major Leagues as a player. And once you get there, it's even harder to stay. Curt could have quietly accepted his trade and moved on, but he chose not to. He took on a cause, because he believed it to be the right thing to do -- not just for himself, but for all those players who would one day follow in his footsteps."

Baseball economics were forever transformed by Flood's fight. The average salary of an MLB player in 2016 was $4.4 million -- nearly 10 times the amount Flood made over his entire 15-year career.

Flood was awarded the NAACP Jackie Robinson Award for contributions to black athletes in 1992, and he received a standing ovation when he appeared at an MLBPA meeting following the 1994 labor stoppage.

Two days after turning 59 years old, Flood died of throat cancer on Jan. 20, 1997. Later that year, Congress introduced legislation that established federal antitrust law protection for Major League players, named the Baseball Fans and Communities Protection Act of 1997.

A year later, Congress introduced a similar legislation, titled the Curt Flood Act of 1998.

"Because he came our way, we are better," Rev. Jesse Jackson said at Flood's funeral. "Baseball didn't change Curt Flood. Curt Flood changed baseball. Curt opened the floodgates."