Baseball Hall of Famer Phil Niekro, who pitched well into his 40s with a knuckleball that baffled big-league hitters for more than two decades, mostly with Atlanta, has died after a long fight with cancer, the team announced Sunday. He was 81.

Atlanta said Niekro died Saturday night in his sleep. He lived in the Atlanta suburb of Flowery Branch, where a main thoroughfare bears his name.

Niekro won 318 games over his 24-year career, which ended in 1987 at age 48 after he made one final start with Atlanta.

Known for a pitch that befuddled hitters and catchers — heck, Niekro didn't even know where it was going — he was a five-time All-Star who had three 20-win seasons with Atlanta.

Niekro also pitched for the New York Yankees, Cleveland and the Toronto Blue Jays late in his career.

"We are heartbroken on the passing of our treasured friend," Atlanta said in a statement. "Knucksie was woven into [the team's] 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."

A statue of Niekro delivering his trademark pitch is located outside of Truist Park, Atlanta's stadium.

Niekro didn't make it to the big leagues until 1964, when he pitched 10 games in relief for the then-Milwaukee. He made only one start over his first three years in the big leagues but finally blossomed as a starter in 1967 — the team's second year in Atlanta — when he went 11-9 and led the National League with a 1.87 ERA.

With a fluttering knuckleball that required catchers to wear an oversized mitt, Niekro went 23-13 as Atlanta won the first NL West title in 1969.

He also had 20-win seasons in 1974 and 1979, despite pitching for a team that fell on hard times after its appearance in the inaugural NL Championship Series, where Atlanta was swept in three games by New York's Amazin' Mets.

Niekro also led the league in losses four straight seasons, losing 20 games in both 1977 and '79.

He finished with a career record of 318-274 an a 3.35 ERA. Niekro was inducted into the Baseball Hall of Fame in 1997.

His younger brother, Joe, also had a long baseball career with an arsenal that included the knuckleball. He won 221 games over 22 years in the big leagues, making the Niekros baseball's winningest set of siblings, with a total of 539 victories, just ahead of Gaylord and Jim Perry.

Joe Niekro died in 2006 at age 61.

With the Blue Jays immersed in a tight division race in 1987, Toronto catcher Ernie Whitt was pleased the club acquired Niekro for the stretch drive.

His one opportunity to catch the 48-year-old knuckleballer came on Aug. 29 that year against the Oakland Athletics at Exhibition Stadium.

"He'd had such a long career and you just knew he was going to be a Hall of Famer," Whitt said. "Just to have the opportunity to catch him, I was excited about it. I was thrilled."

Niekro's appearance didn't last long. He was shelled for five earned runs over two-thirds of an inning in what would be his third and final start as a Blue Jay.

"It's sad. I was very fortunate that I was able to play with him for a little bit," Whitt said. "The way he carried himself as a professional, he joked around and had a good time.

"He was nice to have on our club for that short period of time."

Niekro, while pitching with the New York Yankees, enjoyed a special moment in Toronto less than two years before his brief stint with the Blue Jays. He earned his 300th career win on Oct. 6, 1985 at the Ex, capping the complete game by fanning Jeff Burroughs for the four-hit shutout.

The Blue Jays beat New York a day earlier to clinch the American League East division title. Niekro's appearance in the season finale would be his last as a Yankee.

He joined Cleveland in 1986 and was dealt to Toronto on Aug. 9, 1987 in exchange for Darryl Landrum and Don Gordon. The Blue Jays, Yankees and Detroit Tigers were battling for top spot in the East at the time.

"I think it [showed] the organization was going to try to do whatever they could for us to win the division," Whitt said in a phone interview with The Canadian Press.

"He fit right into the room," he added. "He was just like one of the guys."

Backup catcher Charlie Moore played in Niekro's Toronto debut, a 10-3 loss to the Chicago White Sox. Niekro took the defeat after giving up three earned runs over 5 2/3 innings.

He had a similar line in a 3-1 loss to the California Angels about a week later.

With Whitt moving behind the plate against Oakland, Niekro gave up four hits - including a three-run homer to Carney Lansford - before getting the early hook.

"I was disappointed that he didn't have his good stuff," Whitt said. "It was like, 'Did I do something wrong?' But when you're throwing basically knuckleballs, if it's dancing and it's working, then you're OK. But if it's not, it's pretty easy to centre up if it's not moving."

The Blue Jays would fade down the stretch. Toronto closed the season with seven losses and settled for a second-place finish behind the Tigers.

Niekro would grip the ball with his fingernails on the seams and release the knuckler with almost no spin. Batters could be flummoxed as the ball dipped, dived or floated its way to the plate.

"When you're catching it, you're not really catching it. You're just snagging it," Whitt said. "You're waiting until the last minute and just trying to react to it."

Whitt said Niekro's knuckler would hover between 60 and 75 m.p.h.

"It can make you look very foolish at the plate," he said. "It's no fun to hit and it's no fun to catch."

Whitt recalled that Niekro had a real presence in the locker-room thanks to his vast experience and personality. Old-school all the way, Niekro quickly meshed with his teammates.

"He'd just walk around with a cigarette in his mouth, just nonchalant," Whitt said.

After a game, the knuckleballer would still be sporting his cap while sitting in the hot tub, Whitt recalled, adding Niekro always enjoyed sitting down to talk baseball over a smoke and a cold beer.

"Those days are gone now," Whitt said with a chuckle. "At the end of the game, everyone is out there, out of the ballpark and definitely not drinking beer."