Forsch's wife, Janice, told the St. Louis Post-Dispatch that the former pitcher suffered an aneurysm in his upper chest.
Forsch was at Busch Stadium last Friday, throwing out the ceremonial first pitch prior to Game 7 of the World Series. The Cardinals beat the Texas Rangers, 6-2, to win their 11th World Series title. He was honored as not only one of the franchise's pitchers, but as an instrumental part of the 1982 world champion Cardinals and '85 and '87 pennant-winning clubs.
"Having been with Bob just last week, we are all stunned by this news," said Cardinals chairman Bill DeWitt Jr. "The entire Cardinals organization extends its sincere condolences to Bob's wife, Janice, his two daughters, Amy and Kristin, and his countless friends."
Forsch spent 15 of his 16 Major League seasons with St. Louis from 1974-88, winning 163 games, and is the only Cardinals pitcher to throw two no-hitters. He threw a shutout in Game 1 of the 1982 National League Championship Series, helping propel the Redbirds to their first pennant since '68, and won twice during the '87 postseason.
He regarded that NLCS start as the most memorable of his career, even above the no-hitters. Forsch was drafted in 1968, just as the Cards were winning their third pennant in five years, but then had to wait until '82 before getting his own taste of the postseason in St. Louis.
Forsch, one of 28 pitchers in Major League history to throw multiple no-hitters, was a Minor League pitching coach for the Reds' Rookie League affiliate, the Billings Mustangs, the past three seasons. Only Bob Gibson (251 from 1959-75) and Jesse Haines (210 from 1920-37) have won more games in a Cardinals uniform.
"The Reds family and all of baseball mourn the passing of Bob Forsch," Reds general manager Walt Jocketty said in a statement. "He spent his entire life in baseball and touched many people both inside and outside the game. Over the last few seasons, he played an important part in the development of our young players. Our baseball operations staff and the players he touched will miss him. Our thoughts and prayers are with his immediate and baseball families."
Beyond his ability, though, Forsch was widely regarded as a decent, humble, likable man.
"We are deeply saddened by the sudden passing of Bob Forsch," DeWitt said. "Bob was one of the best pitchers in the history of our organization and a valued member of the Cardinals family."
St. Louis great Ozzie Smith tweeted: "A great competitor/teammate and one of the finest men I played with. Heaven just got a starter."
Forsch threw his first no-hitter against the Phillies on April 16, 1978, and his second one vs. the Expos on Sept. 26, 1983. His were the only no-hitters thrown at Busch Stadium II, the park which stood from 1966-2005.
His brother, Ken Forsch, who pitched for the Astros and Angels during a 16-year career, tossed a no-hitter for Houston against Atlanta on April 7, 1979, making Bob and Ken the only brothers to each pitch a no-run, no-hit game in Major League history.
Hall of Famer Whitey Herzog, the Cardinals' manager from 1981-90, told The Associated Press that he was originally scheduled to throw out the first pitch prior to Game 7, but that he couldn't make it because of health reasons.
"I ... was still on medicine, so they decided Forschie would do it," Herzog said. "We've kept in touch throughout the years. ... It's a real shock.
"I was fortunate to have Bobby on my team. He never missed a turn, pitched 200 innings each year. He'd take the ball, and he was a great competitor."
Drafted by the Cardinals in the 26th round in 1968, Forsch made his Major League debut in July of 1974 at the age of 24. In addition to his pitching, he was a good hitter, batting .213 with 12 homers in his career and winning Silver Slugger Awards in 1980 and '87, becoming one of only seven pitchers in MLB history to win the award multiple times.
Forsch finished his playing career in 1989 after parts of two seasons with the Astros.
Cash Kruth is a reporter for MLB.com. Follow him on Twitter at @cashkruth. Matthew Leach is a reporter for MLB.com. Read his blog, Obviously, You're Not a Golfer and follow him on Twitter at @MatthewHLeach. This story was not subject to the approval of Major League Baseball or its clubs.