Hibernian youth team player David Paul, 18, passed away in the early hours of Sunday, with no suspicious circumstances.
Chairman Rod Petrie said of the promising midfielder: "Everyone at the club is deeply affected by this. David was a talented and promising young footballer, and a fine young man.
"Our thoughts - and the thoughts of the entire Hibernian community - are with his family at this dreadful and difficult time for them.
"Whilst we understand that people will wish to offer their support, we hope that the wishes of the family for privacy will be respected."
Later on Sunday 13-year-old Tynecastle FC player Jamie Skinner – a former member of the Hearts academy – also passed away after collapsing during a match in Scotland’s capital city.
"A tragic event happened at Saughton Astro on Sunday 22nd December 2013 - a young boy playing for the Under-14s, Jamie Skinner, playing the game he loved, lost his life on the pitch,” the club said in a statement.
"In an innocuous event during the game Jamie collapsed and despite the valiant attempts of everyone at the game, and the ambulance service, attempts to revive him were sadly in vain.
"Although Jamie was new to our Tynecastle family, he had up until recently been playing for Hearts, he was a prospect that undoubtedly would have had a bright future in the game.
"No words can fully express our grief and dismay at seeing this happen, we can only pass on all our thoughts and prayers to friends and family and hope they will get some strength from the out pouring of love and support from everyone."
Scottish football suffered a high-profile death almost exactly six years ago when Motherwell captain Phil O’Donnell collapsed with heart failure during an SPL match with Dundee United. He was 35.