Corey Phelan -- a minor league baseball player for the Philadelphia Phillies organization -- passed away after battling cancer. He was only 20 years old.
The team announced the sad news Thursday evening ... saying they are devastated over Phelan's death and described how his "positive presence and selflessness influenced everyone around him".
"Corey is and will always be a special person," Phillies director of player development Preston Mattingly said.
"His smile lit up a room and everyone who came in contact with him cherished the interaction. His memory will live on, especially with the Phillies organization."
The New York native -- who signed with the Phillies org. as an undrafted free agent in August 2020 -- found out about the non-Hodgkin's lymphoma in April after he passed out in the shower.
Phelan underwent scans ... and it was determined he had a 9-inch mass in his chest.
The pitcher received chemotherapy treatment at the Memorial Sloan Kettering Cancer Center in New York after the diagnosis ... and went to visit the team when they played the Mets at Citi Field in May.
"That was one of the best nights ever," Phelan said, "getting to be able to talk with the guys in the locker room, Joe Girardi took me on the field, everyone supportive and nice."
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"The whole Phillies organization has been nothing but amazing to me and my family."
Phelan -- who appeared in 9 games with an 0.93 ERA and 1.14 WHIP -- made his last Instagram post 2 weeks ago, saying "Can’t wait to get back out there🙏🏻❤️"