Reeds had been an assistant with the Senators since 2011. The team first announced he had cancer last year. His cancer was diagnosed as inoperable last month and he was recently hospitalized with pneumonia.
"It is with very heavy hearts that all of us within the Senators family remember Mark who was truly a wonderful father, husband, player, coach and friend," Senators owner Eugene Melnyk said in a statement. "Mark’s charismatic fighting spirit was present right until the end. We are all better for having had the opportunity to work so closely with Mark whose passion for life, hockey and his family will leave an indelible mark on our organization. The entire Ottawa Senators organization sends its deepest condolences to the Reeds family."
Senators general manager Bryan Murray also has cancer. He said in November that his colon cance is incurable.
"I'm not sure how (players) will handle it," Murray said Tuesday, according to USA Today. "I'm hoping that they will handle it as Mark said in his last visit with them, 'Let's win it all.' So we're going to use that, hopefully, in a positive manner."
On Wednesday, the Senators added an "MR" sticker to their helmets for the duration of the playoffs in honor of Reed.
Reeds played 365 NHL games in eight seasons for the St. Louis Blues and Hartford Whalers. He later became a coach for a variety of minor and junior teams. He was hired by the Senators after leading the OHL's Owen Sound Attack to a league championship.
The Senators begin their playoff series against the Montreal Canadiens on Wednesday.
- Dan Gartland