The Phillies announced Thursday that they will retire Dick Allen’s No. 15 in a move that breaks tradition and provides serious momentum for Allen’s candidacy for the Hall of Fame.

Allen, who played nine seasons of his 15-year career with the Phillies, can be voted this winter into the Hall of Fame as part of the Golden Days Committee. His number will be retired on Sept. 3, the anniversary of his major-league debut in 1963 at Milwaukee’s County Stadium. The Phillies also plan to honor Allen in 2021, when they expect fans to return to Citizens Bank Park.

The Phillies had previously said that they would retire numbers only for players enshrined in the Hall of Fame. But retiring Allen’s number just before the voting process could be the boost he needs to make it to Cooperstown, N.Y. Allen was one vote shy in 2014.

“Dick Allen burst onto the 1964 Phillies and immediately established himself as a superstar. His legendary performance on the field gave millions of fans lasting memories, and he helped cement my love for baseball and the Phillies as a young boy,” said John Middleton, the team’s managing partner. “The Phillies organization is thrilled to give Dick and his family this honor that recognizes his Hall of Fame-worthy career and his legacy as one of the greatest Phillies of all time.”

The Golden Days Committee comprises 16 members and includes Hall of Famers, former executives, and media members. The ballot -- which can include players, managers, umpires, and executives -- is reserved for people “whose greatest contributions to the game were realized between 1950 and 1969.”

Allen, Ken Boyer, and Jimmy Wynn are expected to lead the ballot. A candidate must be on three-fourths of the ballots to enter the Hall of Fame.

“[Dick] was a fine ballplayer. He did some great things and hit the ball much further than I did,” Hank Aaron said. “He deserves to be in the Hall of Fame.”

“[Dick] could hit the ball farther than anybody that I’ve seen,” Willie Mays said. “He was, and still is, a Hall of Famer as far as I’m concerned.”

Allen, 78, was the National League’s rookie of the year in 1964 and the American League’s MVP in 1972 with the Chicago White Sox, and was named to seven All-Star teams. From 1964 to 1974, Allen had the fifth-most home runs (319), second-best OPS (.940), and sixth-highest WAR (58.3) of any player.

He was baseball’s best hitter over the first decade of his career, and Allen’s 165 OPS+ from 1964 to 1973 led the majors. That is better than all-time greats such as Hank Aaron, Harmon Killebrew, and Willie McCovey.

From 1880 to 1990, 24 players registered a slugging percentage of .510 or better over at least 6,300 plate appearances. Allen is the only one not in the Hall of Fame.

“Dick played the game like it is supposed to be played,” said Allen’s close friend and former Phillies teammate Tony Taylor, who died last month. “He played the game right. He played the game hard. I used to say to him, ‘God gave you that gift that you have. What you do is a gift from God.‘”

The Phillies’ decision to retire Allen’s number creates the chance that the Phillies could retire the numbers of Chase Utley, Jimmy Rollins, Ryan Howard, or Cole Hamels if they do not reach Cooperstown. The team started following that policy, which is not a formal policy, in the 1980s. But they discarded it Thursday and they may discard it again.

For now, endingthat policy could help Allen finally reach Cooperstown.

“I hope to be a big supporter of his when we get to that point when that committee meets and votes on it,” Mike Schmidt said. “I would think there’s a really good chance that he gets in this year.”

“If you go back in time and analyze Dick’s career and look at his career by applying the modern-day analytics, his numbers are far and above a lot of the guys who are in the Hall of Fame,” Schmidt said.

“That’s always one way to look at it: ‘Well, if he’s in the Hall of Fame, then he deserves to be in the Hall of Fame.’ You’ll go nuts looking at things that way. You’ll also ruffle feathers if you do. But for me, it’s the simplest way to look at it.”