(BLOOMBERG) - The latest bombshell doping violation from track and field has also ensnared the sport's biggest corporate backer: Nike Inc.

Legendary track coach Alberto Salazar, head of the famed Nike Oregon Project, was given a four-year ban from the sport this week for doping rules violations. The lengthy report that accompanied the ruling disclosed emails showing that Salazar and Jeffrey Brown, a Nike-paid physician who was also banned for four years, repeatedly informed Nike executives, including Chief Executive Officer Mark Parker, of what they were doing with drug tests.

The involvement from the highest management level casts a shadow over Nike's vast efforts in track and field. The company does US$4.5 billion (S$6.21 billion) in annual running sales alone, and its marketing within the professional ranks is a large part of that appeal. Nike is the biggest corporate backer of running both in the United States and abroad, with close partnerships with the US Olympic Committee and USA Track & Field, plus international events and national bodies.

"Running is Nike's DNA," said Rick Burton, a sports management professor at Syracuse University and former chief marketing officer for the USOC. "This may cause people to wonder what Nike's objectives are, or why Nike is behaving this way. But I don't think it will change Nike's investment in track and field."

It is too early to tell what impact the sanctions may have on the corporation. The US Anti-Doping Agency (Usada) found that Salazar helped traffic testosterone, a banned substance, and tampered with evidence, but found no evidence that he administered the drugs to runners.

He has denied wrongdoing and says he will appeal. Nike said that it supports his decision to appeal, and that it does not condone doping.

Nike's shares have dropped for three consecutive days amid declines in the stock market. Nike has fallen as much as 3.8 per cent since Monday's close, the biggest three-day decline in two months.

The accusations centre around the Nike Oregon Project, the programme that Salazar helped found in 2001. Based out of Nike's Beaverton headquarters, he has worked with some of the world's top runners, helping win a handful of Olympic medals, but also drawn criticism over training techniques and allegations of doping.

Nike's swoosh looms large over the track world - larger than it does in most other sports. At the 2019 USA Track & Field Outdoor Championships, for example, 72 per cent of the top-three finishers were Nike runners, according to data compiled by LetsRun.com. Among male athletes, it was 87 per cent.

Salazar, a former champion himself who won three consecutive New York City marathons in the early 1980s, has been among the most important figures in preserving that status. He has coached some of the top track athletes in the world, including Olympic medallists Mo Farah and Galen Rupp. The Oregon Project's current runners include Dutch champion Sifan Hassan, who just won the women's 10,000m at the World Championships in Doha, Qatar, and Donavan Brazier, who set a US record in the men's 800m.

As dominant as Nike may have been, the company is facing renewed pressure from rivals like New Balance and Puma, and smaller companies like Oiselle. In 2016, after an 800m runner named Boris Berian agreed to leave Nike for New Balance, Nike sued to keep him in its stable, a lawsuit that called attention to pressures many runners feel to sign with the sport's biggest brands.

At the time, Nike's annual marketing budget for track and field was between US$60 million and US$90 million, and higher in Olympic years, according to the Wall Street Journal.

Earlier this year, several current and former Nike track stars, including nine-time Olympic medallist Allyson Felix, spoke out against the company's pregnancy policy, which they said unfairly punished female runners who decided to have children.

In the aftermath, Felix chose to sign her next sponsorship deals with Gap Inc.'s Athleta brand. In another surprise news from a few months earlier, New Balance signed 20-year-old hurdler Sydney McLaughlin, considered by many to be the future face of US track.

The Usada investigation into Salazar spanned several years, and while the arbitrators recommended punishment, they did not find any evidence that he gave banned substances to any Nike athletes. Instead, they concluded that experiments he conducted on his sons and a former Oregon Project coach, plus instructions he gave regarding the reporting of some treatments, were in violation of the rules.

In its 140-page report, the group of arbitrators says it does not believe Salazar had bad intentions when he broke the rules. In one 2009 email, Nike CEO Parker said he was interested in determining "the minimal amount of topical male hormone required to create a positive test".

Evidence from the arbitrators suggests that Salazar's studies on how much hormone would trigger a positive test was done out of paranoia that someone else would try to sabotage Nike runners.

In a letter sent to employees on Tuesday (Oct 1), Parker said that media reports that he was involved in a doping cover-up were not accurate. "To have my name and Nike's name linked to this reckless characterisation is offensive," he said.

Nike did not respond to a requests for comment.

Salazar is not the first person connected to Nike to go through public doping allegations. The company famously stood by cyclist Lance Armstrong after Usada published a detailed report exposing his doping regimen (he was dropped by the company a week later).

Armstrong's name comes up a number of times in the Salazar report as well - at one point Salazar emails the former Tour de France winner, who was subsequently stripped of his seven Tour titles, with results from one of their tests. "You will finish the Iron Man in about 16 minutes less while taking this," the coach wrote, referring to long-distance triathlon races.

"They've had a history in the past of standing firm when they believe an athlete or a representative of Nike is under challenge," Burton said, citing the example of golfer Tiger Woods' 2009 sex scandal. "For example, Nike was one of the few brands that stayed with Tiger Woods through his entire process."

Salazar was at the World Championships in Doha when the ruling came down and promptly had his accreditation revoked. The ban, however, does not directly affect any Oregon Project athletes, who continue to compete at the event. Hassan, for example, will compete in the 1,500m later this week.

That did not stop other athletes from speaking out, including US steeplechase athlete Andy Bayer, who is a Nike athlete but not part of the Oregon Project team. After advancing to the final in Doha, he expressed anger over the revelations.

"I'm not that surprised, to be honest," he said. "I don't believe that every athlete in that group is dirty, but we need to get drug cheats out of the sport so I'm glad it came to the surface."