Phil Niekro, a pitcher who used his signature knuckleball to fool generations of hitters as well as craft a Hall of Fame career, died Saturday night in his sleep after a long battle with cancer, the Atlanta Braves announced Sunday. He was 81.

Niekro, inducted into the Hall of Fame in 1997, was one of baseball's most prolific and durable pitchers, using his "butterfly" pitch to win 318 games in a career that spanned 24 seasons, 20 of those years with the Milwaukee/Atlanta Braves.

"We are heartbroken on the passing of our treasured friend, Phil Niekro," said the Braves in a prepared statement. "Knucksie was woven into the Braves fabric, first in Milwaukee and then in Atlanta. Phil baffled batters on the field and later was always the first to join in our community activities. It was during those community and fan activities where he would communicate with fans as if they were long lost friends.

"He was a constant presence over the years, in our clubhouse, our alumni activities and throughout Braves Country and we will forever be grateful for having him be such an important part of our organization.

"Our thoughts and prayers are with his wife Nancy, sons Philip, John and Michael and his two grandchildren Chase and Emma."

As it is with many knuckleball pitchers, age proved no barrier to Niekro. He amassed 121 victories after he turned 40 -- a major league record -- and pitched until he was 48. By the end of 1987, his final season, Niekro ranked 10th among major leaguers in number of seasons played. Only Cy Young, "Pud" Galvin and Walter Johnson pitched more innings than Niekro's 5,404. No pitcher since the dead-ball era spent more time on a major league mound.

"Phil Niekro was one of the most distinctive and memorable pitchers of his generation," said MLB commissioner Rob Manfred in a prepared statement. "In the last century, no pitcher threw more than Phil's 5,404 innings. His knuckleball led him to five All-Star selections, three 20-win seasons for the Atlanta Braves, the 300-win club, and ultimately, to Cooperstown.

"But even more than his signature pitch and trademark durability, Phil will be remembered as one of our game's most genial people. He always represented his sport extraordinarily well, and he will be deeply missed. On behalf of Major League Baseball, I extend my condolences to Phil's family, friends and the many fans he earned throughout his life in our National Pastime."

The symbol of both the success and longevity of Niekro's career was the knuckleball, that whimsical floater that baffles not only hitters and catchers, but also the pitchers who never really know how the rotation-less pitch will dance toward the plate.

Niekro was the king of the knuckleballers, ranking first in victories and strikeouts (3,342). Tom Candiotti, a notable knuckler in his time and former teammate of Niekro's with the 1986 Cleveland Indians, said that talking to "Knucksie" was "like talking to Thomas Edison about light bulbs."

If staying in the majors could be owed to the knuckler, the same might be said of Niekro's initial difficulty in reaching the big leagues. Perplexed catchers and managers wary of passed balls and wild pitches were reasons often cited for Niekro's extended stay in the Braves' minor-league system. Signed in 1958, he didn't break through for good for nearly a decade. Yet the knuckler was all Niekro had, all he believed in.

"I never knew how to throw a fastball, never learned how to throw a curveball, a slider, split-finger, whatever they're throwing nowadays," he said. "I was a one-pitch pitcher."

First called up by Milwaukee in 1964, Niekro see-sawed between the majors and minors, a pitcher struggling to find a niche, and willing catchers. He found both in 1967, when he was united with Bob Uecker, a veteran reserve backstop with many quips, and sage advice.

"Ueck told me if I was ever going to be a winner to throw the knuckleball at all times and he would try to catch it," said Niekro. "I led the league in ERA (1.87) and he led the league in passed balls."

Uecker acknowledged he did a lot of chasing.

"Catching Niekro's knuckleball was great," said Uecker, now a Hall of Fame announcer. "I got to meet a lot of important people. They all sit behind home plate."

By 1969, Niekro was an All-star. His 23 victories that season earned him a second place in the National League Cy Young Award vote. He would go on for two more decades living inside hitters' heads. "There aren't many hitters who like facing knuckleball pitchers," he said. "They may not be intimidated by them, but they sure are thinking about them before they go into the box."

"Trying to hit Phil Niekro is like trying to eat Jell-O with chopsticks," said Bobby Murcer.

"He simply destroys your timing with that knuckleball," said Hall of Famer Ernie Banks. "It comes flying in there dipping and hopping like crazy and you just can't hit it."

"It actually giggles at you as it goes by," said Rick Monday.

Niekro, born in Blaine, Ohio, on April 1, 1939; was the proud scion of a family dynasty of sorts. Phil Niekro Sr., a laborer and part-time semi-pro pitcher, had mastered the knuckler after an arm injury threatened to end his playing days. He would teach his sons, Phil Jr. and Joe, the pitch when they were youngsters. Phil and Joe, known as "Knucksie" and "Little Knucksie," respectively, learned well, going on to pitch a total of 46 major-league seasons, earn six All-Star Game berths and, in perhaps their proudest achievement, combine for 539 victories.

Their win total still stands as a major-league record for siblings, as they surpassed another brother combination featuring a Hall of Famer: Gaylord and Jim Perry (529 wins combined).

Though Phil and Joe Niekro did twice team together, with the 1973-74 Braves and the 1985 Yankees, the two self-declared best friends were more often friendly rivals. In 1979, Phil, pitching for the Braves, and Joe for the Astros, tied for the most victories in the National League, with 21 each. They clawed against each other as mound opponents, with Joe defeating his big brother, 5-4, in their careers. That edge was made possible by a game-winning home run Phil gave up to Joe, the only homer Joe hit in his 22-year career.

When Phil Niekro won his 300th game, Joe was at his side, and it was arguably the most unique victory of the elder brother's career. It was Oct. 6, 1985, the final day of the season. The Yankees had fallen short of the postseason the day before with a loss in Toronto. In the finale, manager Billy Martin handed pitching coach duties to Joe Niekro and the ball to Phil Niekro. Phil, trying for a fifth time to win No. 300, entered the bottom of the ninth having shut out the Jays on curveballs, slip pitches, fastballs and screwballs -- everything but a knuckleball.

He would say later that he wanted to prove he was a pitcher, not just a knuckleballer. Then sentiment finally took over with two outs in the ninth. Facing Jeff Burroughs, an old friend and former Braves teammate, Phil Niekro threw four pitches - the final three knucklers. Burroughs struck out, giving the Yankees an 8-0 victory and Niekro his milestone.

"I figured if there's any way I'm going to win my 300th game by striking the guy out, I was going to do it with the pitch that won the first game for me," said Niekro.

Phil Niekro's playing days ended in 1987, but he would don a uniform one more time, as manager of the women's barn-storming Colorado Silver Bullets (1994-1997). His pitching coach? Joe Niekro.

Phil Niekro was preceded in death by Joe Niekro, who suffered a fatal brain aneurysm in 2006.