Mr. Craig was a colorful, old-school baseball lifer who looked like President Lyndon B. Johnson and prodded his players with his signature, folksy expression, “Humm Baby.” During a mound visit, he once told a struggling pitcher, “Get him out. I need a beer.” (The result of the at-bat is not known.)

After winning the World Series with the Dodgers in 1955 and 1959, Mr. Craig picked up a third ring with the St. Louis Cardinals in 1964. In between, he was the ace for the hapless New York Mets, who lost 12o games during their inaugural season in 1962 and are considered the worst team in baseball history.

Mr. Craig lost 46 games in two seasons with the Mets, including 18 straight in 1963. At one point, he changed his number from 38 to the typically unlucky 13 just to change his fortune.

Following his retirement in 1966, Mr. Craig became a scout and pitching coach. He took over as manager of the San Diego Padres in 1978 but was fired two years later. Detroit Tigers manager Sparky Anderson picked him up as a pitching coach.

By that time, Cubs pitcher Bruce Sutter was already throwing the split-finger fastball, a variation of a forkball in which pitchers split their index and middle fingers wide and parallel to the seams. The grip causes the ball to appear like a fastball and dive as the batter tries to swing.

When Mr. Craig was managing the Padres, Sutter showed him the pitch one day before a game, according to Tyler Kepner’s book “K: A History of Baseball in Ten Pitches.” Mr. Craig then taught it to a couple of Detroit players, including Jack Morris.

The first few times, nothing happened when Morris threw it. Mr. Craig suggested a couple adjustments.

“So I threw about three more and the fourth one was just — whomp, straight down,” Morris told Kepner. “And immediately I go, ‘Holy s---, this is like cheating. If I get this down, there ain’t nobody alive gonna hit it.’”

Morris became a Hall of Fame pitcher.

“There ain’t no doubt about it — and you can call me cocky — but if it is thrown properly, there’s no one living who can even hit it, and if they do, it will be a groundball,” Morris told Sports Illustrated. “I don’t throw it perfect all the time, but I have to give that pitch a lot of credit. It’s turned me into a strikeout pitcher.”

Mr. Craig taught the split-finger to other pitchers and coaches. Eventually, it became the most popular pitch in baseball during the 1980s. The pitch fell out of favor in the 1990s after some pitchers who threw it a lot developed elbow problems, though many splitter hurlers disputed the connection.

“I think it’s one of the easiest pitches in the world on your arm, because you don’t change anything,” Curt Schilling, a split-finger pitcher, told Kepner. “My elbow doesn’t do anything other than what I do on my fastball for the most part. It’s the easiest pitch to learn, easiest pitch to teach, and in my mind one of the easiest pitches to throw.”

Pitchers still turn to it, especially those struggling to get outs.

Erik Swanson, a Toronto Blue Jays reliever who began using a splitter a couple seasons ago after a rocky start in the big leagues, told the Athletic that the pitch “saved my career.”

Roger Lee Craig was born in Durham, N.C., on Feb. 17, 1930, and was the eighth of 10 children. His father sold shoes, and his mother worked in a nursing home.

At 6 foot 4, he played basketball and baseball in high school, winning a hoops scholarship to what is now North Carolina State University. In 1950, he left school to join the Dodgers, and he made it to the major leagues in 1955, when he was called up from Triple-A during the pennant race.

In the World Series that year against the New York Yankees, Mr. Craig was the winning pitcher in Game 5, giving the Dodgers a 3-2 edge in the series.

During his 12 seasons pitching in the big leagues, he was 74-98 with 3.83 ERA. Almost half of his losses came during his two seasons with the horrible Mets.

In 1951, he married Carolyn Anderson. In addition to his wife, survivors include four children; seven grandchildren; and 14 great-grandchildren.

The Giants were the laughingstock of baseball when Mr. Craig took over in the final days of the team’s 100-loss season in 1985.

Two years later, the Giants won their first division title in 16 years. Suddenly, they were postseason stars.

Before Game 1 of the playoffs, The Washington Post reported that a national TV producer told Mr. Craig, “We’ll have a camera on you, so don’t pick your nose.”

“Whadaya mean?” he replied. “That’s one of my signs.”