Francisco Garcia, 21, had been working with Malaga-based Atletico Portada Alta since 2016 and was the manager of their junior team.
Mr Garcia was taken to hospital with severe coronavirus symptoms and there was diagnosed with a form of leukaemia.
The Sun is reporting that the young coach is the fifth victim of the Covid-19 pandemic in the Malaga region but is by far the youngest – others have been in their 70s or 80s.
Nearly 300 people have died in Spain.
It was only after Mr Garcia arrived at hospital that doctors diagnosed him with leukaemia. The condition made him acutely vulnerable to the Covid-19 virus.
In Spain, football including top-flight La Liga has already been suspended to protect players and slow the spread of the virus.
Heartbroken Portada Alta president Pepe Bueno said: "Francisco was a great guy and a very talented coach. We are all still shocked.
"The hospital rang me at 7pm on Sunday to say his condition had stabilised, but then an hour later...
"The coronavirus came together with a bad illness he had. I can't believe it has happened."
Portada Alta said in a statement on Instagram: "We wish to express our deepest sympathy to the family and friends of Francisco Garcia, who has left us today.
"What will we do without you, Francis?
"We will never forget you. Rest in peace, legend."
A further 18 cases of the coronavirus have been confirmed in Scotland bringing the total to 171, according to government officials.
The recent figures cover the cases diagnosed in the last 24 hours, the Scottish Government reports.
Currently the most affected area in Scotland is Greater Glasgow and Clyde with 44 cases.
A number of Scottish schools had to close this morning as cases are on the rise across the country.