The BBC reports that Fleck is "in good health" but exactly what caused him to collapse is unknown.
The two incidents are not isolated. In fact, there have been a number of similar moments involving elite athletes.
German newspaper Berliner Zeitung catalogued them in an article headlined: "Puzzling heart diseases in football."
The article listed 21 incidents from "recent weeks and months" involving players, coaches, a referee and even a sports director who collapsed, suffered a heart attack, or sadly died from heart problems during a match.
"An unusually large number of professional and amateur soccer players have collapsed recently," the article reads.
"The professional player Sergio Agüero from FC Barcelona will be out for at least three months. The 33-year-old had been substituted for the game against Deportivo Alavés with breathing problems.
"He was holding his chest and was admitted to a hospital. He is now being treated by a cardiologist for heart problems. At the European Championship, the player Christian Eriksen collapsed in front of the cameras. Diagnosis: cardiac arrest."
Berliner Zeitung noted that "sudden cardiac death during exercise has 'different triggers'".
The incidents have been seized upon by conspiracy theorists who say the Covid-19 vaccine is to blame.
Athletes have expressed concern, and a right-leaning political party in New Zealand — the Outdoors Party — linked vaccines to 90 apparent medical emergencies involving athletes across two dozen countries.
But the mass hysteria is unfounded. As the ABC's fact checkers discovered, many of the names on those lists died from "heatstroke, on-field collision, apparent suicide" and that "athletes" included a golf caddie and retired players.
Dr Jonathan Drezner, from a group of doctors monitoring heart conditions among athletes during the pandemic, told the ABC that linking the vaccine with deaths on the sporting field was "misinformation" and there has "not been an increase in sudden cardiac arrest or death in young athletes".
The Australian Technical Advisory Group on Immunisations (ATAGI) monitors reports of rare but "potentially serious adverse events following immunisation, including heart problems such as myocarditis and/or pericarditis".
"These conditions can occur in the absence of vaccination and are also a recognised complication of COVID-19," ATAGI says.
The TGA publishes a report weekly detailing the estimated rate of myocarditis after first and second doses by age and sex.
It notes: "The observed rates in Australia are consistent with international data. These data show a higher rate in younger individuals (particularly younger males) and following second doses. Most reported cases have been mild, self-limiting and have recovered quickly, although further follow-up of these cases is ongoing. ATAGI noted that a small number of cases were more severe, requiring hospitalisation."
ATAGI has from the beginning declared that the benefits from Covid-19 vaccination "strongly outweigh the risks of myocarditis and/or pericarditis for any age group".
