Wes Unseld’s calling card during a Hall of Fame career in the National Basketball Association was not a majestic jump shot or a slick crossover dribble or a thunderous dunk — it was the precise, bone-crushing picks he set on opposing defenders, inevitably freeing up one of his teammates for a score. His impact was measured less in points and rebounds than in bruises.

“I don’t know of anybody who ever set a meaner screen,” former shooting guard Doug Collins of the rival Philadelphia 76ers once said of him.

Mr. Unseld, who died June 2 at 74, was the most important figure in the history of the franchise that morphed from the Baltimore Bullets to the Washington Bullets to the Washington Wizards. The cause was complications from pneumonia, the team announced. No other details were immediately available.

Mr. Unseld’s name is virtually synonymous with the Bullets. As an undersized but legendarily tenacious center, he was the team’s foundation during its greatest run of sustained success — the 12-year stretch beginning with his rookie season of 1968-1969, during which the team made 12 straight playoff appearances and won its lone championship, over the Seattle SuperSonics, in 1978.

He played 984 games, the entirety of his NBA career, for the Bullets (the team changed its name to the Wizards in 1997) and remains the franchise’s all-time leader in rebounds and was No. 1 in assists until being surpassed by John Wall in 2016. After his playing career ended in 1981, he served the franchise for 23 more years as an executive, broadcaster, head coach and general manager.

Listed officially at 6-foot-7 and 245 pounds, Mr. Unseld frequently gave up four to six inches in height to the opposing center, but he nonetheless packed remarkable physical force into that body through raw strength and willpower.

He also possessed a deceptive athleticism, at least as a younger player, occasionally stunning teammates during practice with a unique trick: He would jump to pluck a rebound from the glass and, before touching the floor again, fling an outlet pass downcourt that would hit the backboard at the other end.

Tales of Mr. Unseld’s toughness and selflessness are legion. His arthritic knees became so bad, he often skipped a week’s worth of practices, as well as pregame warmups, because he could tolerate the pain only for the two hours of game time. Once, he suited up just minutes after having 200 cubic centimeters of fluid drained from his left knee.

“The most amazing thing to me is how effective he was with those bad knees,” teammate Mitch Kupchak told The Washington Post in 1996. “Any time he stepped on the floor, whether it was for practice or a game, he was in pain. It wasn’t comfortable for him, but he saw it as part of his job. He knew his teammates were watching him and if he didn’t do it, they might not do it. We always talk about leadership in sports, but you don’t designate yourself a leader. You just lead. That’s what Wes did.”

Mr. Unseld averaged just 10.8 points per game during his 13-year career, or 14 points fewer than his contemporary Kareem Abdul-Jabbar of the Milwaukee Bucks and Los Angeles Lakers.

He was a prolific rebounder, averaging 14 per game for his career and leading the NBA in 1974-1975, but his biggest contributions were invisible on the stats sheets: his pinpoint outlet passes to start the offense back down the court, his suffocating defense against opposing centers such as the Lakers’ Wilt Chamberlain and the New York Knicks’ Willis Reed and — of course — those devastating picks, in which he used positioning to block a defender from covering a teammate open for a shot.

“People ask me how tough Russell and Chamberlain were,” Reed said at Mr. Unseld’s Hall of Fame induction in 1988. “They don’t understand how much this man [Unseld] abused your body.”

Asked once about his modest stats, Mr. Unseld replied: “It’s not my job to look good. It’s my job to make other people look good.”

Another time, he explained to The Post his approach on the court: “I know that night in and night out the guy I play against will have more physical ability. But I feel like if I go out against a guy and play him 40 or 48 minutes, toe to toe, head to head, he is going to get tired or beat up or bored for two or three minutes. That will be enough to make sure he doesn’t win the game for his team.”

From Louisville to Baltimore

Westley Sissel Unseld was born in Louisville on March 14, 1946, and was one of nine children, including two who were adopted. His father was a factory worker and a former semiprofessional baseball player and boxer. His mother was a school lunchroom manager.

Mr. Unseld led Louisville’s Seneca High School to a pair of state championships in the mid-1960s. In the days before most athletes lifted weights, he worked in a steel-supply business as a teenager, perhaps helping account for the strength he displayed as an NBA center.

Coming out of high school, he was recruited by the University of Kentucky’s Adolph Rupp, one of the winningest coaches in college basketball, who was being pressured to integrate the school’s all-white team. Mr. Unseld, who reportedly received racial threats, said he went instead to the University of Louisville in part to be closer to his father, who had suffered a heart attack. He was twice named an all-American at Louisville, graduating in 1968.

The Bullets, then playing in Baltimore, made Mr. Unseld the second overall pick of the 1968 NBA draft — behind only Elvin Hayes of the University of Houston. Mr. Unseld’s arrival changed the trajectory of the franchise almost overnight — the Bullets jumped from sixth place in their division to first place in his rookie season. He was just the second player in history, following Chamberlain, to be named rookie of the year and most valuable player in the same season.

By 1971, the Bullets had made it to the NBA Finals, where they were swept in four games by the Milwaukee Bucks, led by Abdul-Jabbar and Oscar Robertson, a future Hall of Fame guard. Afterward, General Manager Gene Shue decided the team needed an elite scorer and traded for the Houston Rockets’ Hayes, the player picked one spot ahead of Mr. Unseld in the 1968 draft.

It took six more years, and a handful of playoff flameouts before the Unseld-Hayes Bullets finally secured the franchise’s first — and still only — NBA title, beating Seattle in seven games in 1978. Before the decisive Game 7, Mr. Unseld, 32 at the time, gathered his teammates in the Bullets’ locker room.

“This is my 10th year, and this might be the last chance I have to win a championship,” he told them, according to The Post. “I just want everyone to know I’ll be there for you today. I don’t care what it is. You don’t have to worry about anything.”

After the Bullets prevailed, an emotionally exhausted Mr. Unseld said, “What I feel is relief.”

Back on the court as coach

After retiring three years later, Mr. Unseld immediately shifted to an executive position in the Bullets’ front office, one he held until team owner Abe Pollin asked him to become head coach midway through the 1987-1988 season.

Those Bullets teams were short on talent and wins, and Mr. Unseld struggled to instill his brand of work ethic and professionalism in younger players. Once, when Mr. Unseld thought 7-foot-7 center Manute Bol wasn’t giving enough effort in the first half of a game, he confronted Bol in the locker room at halftime, lifted him off the floor and jammed his head through a ceiling tile, The Post reported.

When Mr. Unseld stepped down from the coach’s job after the 1993-1994 season — with a career mark of 202-345 in just under seven years — he went back to the front office, eventually becoming general manager in 1996. Chicago Bulls superstar Michael Jordan came out of retirement to serve as president of basketball operations, then played his final two seasons for the renamed Wizards, but the team did poorly and failed to make the playoffs for six years in a row. Mr. Unseld stepped down in 2003.

“For seven years, he had more than his share of knuckleheads, louts, losers and prima donnas,” former Washington Post sports columnist Michael Wilbon once wrote of Mr. Unseld’s checkered tenure as head coach. “Unseld’s biggest misfortune,” Wilbon added, “was not being able to coach a Wes Unseld at any position.”

Survivors include his wife, the former Connie Martin, and two children, Kimberly and Wes Unseld Jr., who has been an assistant coach with several NBA teams.

His wife operated a private elementary school in a poor Baltimore neighborhood for many years. After retiring from the Wizards, Mr. Unseld often mowed the grass, mopped the floors and shot baskets in the gym with students at the school.

“When I retired from basketball, I was interested in what my wife and daughter were doing at the school,” he told Washingtonian magazine in 2015. “Every morning, I sit at the front. I make sure the kids [as they come in] make eye contact, say hello, take their hats off. Be ladies and gentlemen. If a kid does get out of hand, they’re sent to me. But we have a great group of kids. Do they know who I am? Some Google me and are all surprised. The little ones, they don’t know basketball from Dr. Seuss.”

Correction: An earlier version of this story incorrectly reported that the Washington Bullets changed their name to the Wizards in 1995. Owner Abe Pollin announced that he would change the team’s name that year, but the franchise became known as the Wizards only in 1997.