St. Louis Cardinals pitcher Darryl Kile was found dead in his team's hotel in Chicago on Saturday.
Kile, a 20-game winner two seasons ago, was 33.
A spokesperson for the Chicago medical examiner's office confirmed the death on Saturday afternoon, but provided no details about the cause of death, although police said there were no signs of forced entry or foul play.
"It appears he died in his bed, in his sleep," said Michael Chasen, commanding officer of the police's Area Three Homicide.
Dr. Jim Loomis, the Cardinals' assistant team physician, said Kile showed no health problems during a routine physical in spring training and did not have a history of heart problems.
Kile's father died shortly after having a heart attack in his mid-40s in 1993.
An autopsy on the pitcher was planned for Sunday.
The Cardinals were scheduled to play the Cubs on Saturday afternoon, but Cubs player representative Joe Girardi addressed the crowd and said the game had been officially cancelled due to a "tragedy in the Cardinals family."
"My deepest sympathies go out to Darryl's family, his friends and the St. Louis Cardinals ballclub. All of baseball mourns his passing," Major League Baseball commissioner Bud Selig, who cancelled the game, said in a statement.
Several Cardinals players walked out of the team clubhouse in a daze following the announcement. None made any comment, but the Cardinals are expected to make an announcement later Saturday.
"Our club is just totally staggered, I mean, devastated," said a tearful Cardinals manager Tony La Russa. "You guys know what a pro he is."
Kile is survived by his wife, Flynn, five-year-old twin son and daughter and infant son.
The news of Kile's death came just four days after the passing of legendary St. Louis broadcaster Jack Buck.
Kile, who was slated to start Sunday's game, was 5-4 in 14 starts this season for St. Louis with a 3.72 ERA. The six-foot-five pitcher was traded from Colorado to St. Louis after the 1999 campaign, and went 41-24 in two-plus seasons with the Cards, including winning a career-best 20 games in 2000.
Over his 12-year career, Kile posted a 133-119 mark with a 4.12 ERA in 359 games, including 331 starts. He spent his first seven seasons in the majors with the Houston Astros before signing with Colorado, where he pitched for the next two seasons.
"I couldn't believe it, and I still don't believe it," said Cubs manager Don Baylor, who managed Kile in Colorado. "DK was a very special player. He was always the perfect teammate to all the guys who played with him."
Kile had his best season in 1997 with Houston, compiling a 19-7 record in 34 starts with a 2.57 ERA and 205 strikeouts.
He was selected to three All-Star Games during his career (1993, 1997, 2000). Known for his devastating curveball, Kile's career highlights also included a no-hitter against the New York Mets while he wore a Houston Astros uniform.
"In my mind, I can see Darryl Kile right next to me," said Montreal Expos third baseman Fernando Tatis, a former teammate of Kile's in St. Louis. "We always joked together. I can't believe he's dead."
"I have to see it to believe it. We have to realize that he's dead, but in my mind, he's alive because he was one of the greatest," he said.
"I think we've all heard what he was like as a teammate, and it's all true," Colorado Rockies slugger Larry Walker, of Maple Ridge, B.C., said as he wiped tears from his eyes. "He was a great guy, was in a good mood all the time and was a professional at everything in life. It's going to be hard to deal with."
With files from Sport Network and Associated Press