Hal Carlson was a veteran starting pitcher acquired by the Cubs in 1927 from the Pittsburgh Pirates. He pitched for them for several seasons, and didn't make much of an impact. He had a pretty high ERA, and his record was under .500, but in 1930, the Cubs were the defending NL Champs, and had an offense that would have made any pitcher happy to take the mound on their behalf.
Carlson was having a very good season.
But one night in late May, the 38 year old started having horrible stomach cramps. He had been suffering from ulcers for a couple of years, so he wasn't too worried about it at first. But when the pain got worse, he called teammates Riggs Stephenson, Kiki Cuyler, and Cliff Heathcoate asking for them to come to his apartment and help.
When they saw what kind of pain he was suffering, his teammates called the team doctor, but it was too late. By the time the doctor arrived at the apartment, there wasn't anything he could do.
Carlson died that night of a stomach hemorrhage. The Cubs dedicated the season to their fallen comrade, but just a few days after Carlson died, star second baseman Rogers Hornsby broke his leg.
Still, the Cubs fought on.
On September 6, they had a 4-game lead, with only 19 games to play. But third baseman Les Bell hurt his arm, and the team seemed to fall apart. They got swept in Brooklyn, and by September 12th, they had dropped out of first place, never to return.