The emotional response to the death of Antonio Puerta, a 22-year-old midfielder with Spain’s Sevilla FC, has been quite extraordinary. Puerta collapsed during a Spanish league game on August 25 and died three days later in the hospital after several prolonged periods of cardiac arrest.

Puerta was a local boy, born in the working class district of Sevilla, and over 10,000 people — fans from both Sevilla FC and its crosstown rival Real Betis — filled the streets of Sevilla for his funeral.

The grief for Puerta, for his family, and for his pregnant partner was overwhelming. Tributes from big-name soccer stars and dignitaries poured in, and when Sevilla played AC Milan Friday, both teams wore black armbands and carried the name Puerta on their shirts.

As the intensity of the mourning for Puerta began to soften, the sport of soccer was jolted by two more deaths: Chaswe Nsofwa, a 26-year-old Zambian, collapsed during a training session with his Israeli club Hapoel Be’er Sheva, and Anton Reid, a 16-year-old with the Walsall club in England, died after collapsing during a warm-up session.

It seems highly likely that both Reid’s and Nsofwa’s deaths were — like Puerta’s — the result of heart attacks. The drama of Puerta’s collapse and the subsequent frantic rush to get him to the waiting ambulance were quickly chronicled on YouTube. Clive Clarke, a defender for England’s Leicester City club, had watched the images before taking the field for a game in Nottingham one week ago. At halftime, Clarke collapsed and was taken to the hospital. The game was called off.

Clarke was the lucky one. He is recovering from his encounter with cardiac arrest. But how many more such cases of undiscovered heart defects are out there, waiting to turn into tragedy?

The key word, of course, is “undiscovered.” The demands of sports at the pro level surely require that clubs conduct extensive medical testing on their players. Sevilla FC reported that Puerta had indeed passed a whole battery of physical checkups. His fatal problem, according to the Spanish press, was a weakness in the right ventricle, something that was unlikely to show up in medical tests. According to Jiri Dvorak, FIFA’s chief medical officer, sports in general have about one thousand cardiac arrest deaths a year — that takes in all sports, at all levels. Dvorak, along with other medical experts, believes the time has come to conduct extensive screening of soccer players. Such a scheme was organized by FIFA before last summer’s World Cup in Germany. “We set a new standard,” said Dvorak, “with state of the art tests for all [736] players, including electro- and echocardiograms.”

It is claimed that screening of athletes in Italy, the only country where it is compulsory, has resulted in a dramatic lowering of sudden cardiac deaths. In the Veneto region of northern Italy, where screening was introduced in 1981, the incidence of such deaths per 100,000 athletes has dropped to 0.4 from 4.

The program used in Italy includes electrocardiograms, along with checks on an athlete’s personal and family medical history. But screening is not universally accepted as a practical answer to the problem of cardiac arrest deaths. Electrocardiogram evidence is regarded by some experts as unreliable — it did not pick up Puerta’s fatal defect, for instance. Others feel that the cost of screening would prevent its widespread application, but such concerns were played down by Dr. Domenico Corrado of the University of Padua medical school, who said that the cost per athlete was roughly $82.

On one point there was general agreement: The benefits of regular sporting activity — not least among them, a healthy heart — far outweigh the very slight risks involved. As for soccer, it seems to have weathered the storm well. “It is not the sport itself that is the cause of this increased mortality,” said Corrado. It merely triggers ventricular arrhythmia in those who already have a latent heart problem.

A comforting conclusion for soccer, but one that is open to questioning on two fronts. Michel Platini, the former French star who is now the president of UEFA, the body that controls European soccer, quickly saw that “these accidents on the field will probably bring up the problem of the calendar.” He was referring to the sport’s relentless drive to play more games and pointed out that “We all want to play less but … the system is made so that the players play more and more.”

Compounding the exhaustion brought on by too many games is the way in which soccer has changed over the past two or three decades. The sport is now played at a much faster tempo than it has ever been. We may chuckle at the shorter shorts and the longer hair on tapes of games from 20 years ago, but there’s no avoiding the fact that the action looks slow.

The modern player is calculated to cover some 5 or 6 miles during a 90-minute game, not an overwhelming amount, but it is the sheer intensity of the bursts of running, combined with the increasing likelihood of damaging body contact, that is new.

And the body contact gets more severe because soccer’s players are getting bigger. This is partly a natural consequence of a world trend toward bigger bodies, but it also results from the way that soccer, ever since the 1970s, has allowed itself to accommodate higher levels of physical contact.

Within that picture lurks another danger for the sport: drugs. So far, soccer has had a relatively light confrontation with doping. FIFA has just proudly announced that at the recent under-20 World Cup staged in Canada, 208 urine samples were tested for banned substances. All were negative. In a sport that has traditionally relied on agility, quickness, and skill, that makes sense.

But there are those who suspect that drugs may already be a factor in some cases of sudden death in soccer. Those suspicions can only grow if the sport continues its newfound love affair with size and stamina, for those are qualities that bring with them the siren calls of steroids and blood doping.