Phillies players and personnel were informed of the news by club president David Montgomery in a somber pregame meeting.
In a hallway outside the visiting clubhouse, Montgomery fought back tears as he addressed a large group of reporters who had assembled after hearing Kalas had been stricken.
"Sadly, I must confirm that we lost Harry. We lost our voice today. Harry loved our game and made a tremendous contribution to our sport, and certainly to our organization," Montgomery said.
The Phillies had been scheduled to visit the White House today, but Montgomery said the visit had been postponed indefinitely.
The Phillies won the game, 9-8, and dedicated the win to Kalas.
"He's our angel now," outfielder Shane Victorino said after the game. "I'm sure he was calling the game from upstairs."
Montgomery described the players as stunned after receiving the news.
"They treated this as news of a tragedy that happened to a teammate," he said. "Harry was like a teammate to them."
The Nationals organization, hosting its home opener, honored Kalas' memory with a moment of silence before the first pitch.
"He was the heart and soul of the Phillies organization," the stadium public-address announcer told the crowd.
As Kalas' picture flashed on the video board above right field in the hushed stadium, a fan shouted: "We love you, Harry."
Chris Wheeler, a longtime broadcast partner of Kalas', wondered if the Phillies could have played if the game weren't on the road.
"It would have been hard to play if this had been a home game," Wheeler said.
The team did not say how the broadcast team will be affected by Kalas' absence.
Wheeler recalled that he joined the Phillies in 1971, the same year as Kalas.
