Story highlights Players union says MLB is interviewing players, who have attorneys

Ryan Braun sticks by his denial: "The truth hasn't changed"

ESPN: If the suspensions hold up, it could be the biggest scandal in U.S. sports history

Baseball's highest-paid player, Alex Rodriguez, may face suspension

Major League Baseball is set to suspend some 20 players in the coming weeks due to a scandal involving performance-enhancing drugs, according to an ESPN report that said a key figure in the case is now ready to cooperate with investigators.

The network says it is potentially the worst drug-abuse case in the history of U.S. sports.

The league declined to comment to CNN but confirmed that an investigation is in the works.

The players union said Wednesday that players are being interviewed by baseball officials and are represented by attorneys.

"The commissioner's office has assured us that no decisions regarding discipline have been made or will be made until those interviews are completed," the union said in a written statement.

Baseball's highest-paid player, New York Yankee third baseman Alex "A-Rod" Rodriguez, as well as Ryan Braun of the Milwaukee Brewers, are among those facing suspension, ESPN said , citing unnamed sources.

Both have denied recently using performance-enhancing drugs, or PEDs. Rodriguez has admitted in the past to using banned substances when he played with the Texas Rangers in the early 2000s.

Photos: Photos: Drug scandals in sports Photos: Photos: Drug scandals in sports Drug scandals in sports – New York Yankees star Alex Rodriguez was suspended in August 2013 after he was accused of having ties to Biogenesis, a now-defunct anti-aging clinic, and taking performance-enhancing drugs. The suspension covers 211 regular-season games through the 2014 season. Rodriguez denied the accusations and said he intends to appeal. Twelve other Major League Baseball players received 50-game suspensions without pay in the Biogenesis probe, and In July, Milwaukee Brewers star outfielder Ryan Braun was suspended for the rest of the season for violating the league's drug policy. Hide Caption 1 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – Lance Armstong was stripped of his seven Tour de France titles and banned from professional cycling in October 2012 after being accused of using performance-enhancing drugs. Armstrong confessed in January 2013 to doping during his cycling career. Hide Caption 2 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – Barry Bonds is baseball's all-time home run leader, but some commentators say there should be an asterisk by his record. Though he's said he never knowingly used steroids, two San Francisco reporters wrote a book alleging he used performance-enhancing drugs. He was indicted on charges of perjury and obstructing justice for allegedly lying to a grand jury investigating steroids, and convicted of obstruction of justice. Hide Caption 3 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – Lyle Alzado was known as one of the most vicious lineman to ever play the game, and he chalked up more than 100 sacks and almost 1,000 tackles. Before his death from brain cancer at age 43, he told Sports Illustrated he began using steroids in 1969 and that, "On some teams between 75 and 90% of all athletes use steroids." Hide Caption 4 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – Known as "Rocket" for his aggressive pitching style, Roger Clemens played pro ball for more than two decades, racking up seven Cy Youngs. He left Major League Baseball under a cloud of steroid allegations, despite a court finding him not guilty of perjury when he told Congress he never used the drugs. Hide Caption 5 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – At 6-foot-5 and 260 pounds, Alistair Overeem is known for putting mixed martial arts star Brock Lesnar into early retirement. Ahead of a heavyweight title match against UFC champion Junior dos Santos in May, Overeem tested positive for elevated levels of testosterone and was yanked from the card. Hide Caption 6 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – An early and chief accuser of Armstrong, Floyd Landis was himself stripped of his 2006 Tour de France title after testing positive for performance-enhancing drugs. He admitted doping in 2010, the same year he accused many other riders of doping as well. Hide Caption 7 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – As the most decorated Olympian ever, with 22 medals, Michael Phelps is known as a fish in human's clothing, but for a brief period in 2009, after a photo of him smoking a bong was made public, he also was known as a pothead. Despite losing sponsors, he quickly became known for swimming again, securing six medals in the 2012 Games. Hide Caption 8 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – Marion Jones was a world champion track and field athlete who won several titles in the 1990s and five medals during the 2000 Olympic Games in Sydney, Australia. After admitting in 2007 that she had taken performance-enhancing drugs, she was stripped of the gold medals and other honors won after the 2000 Games. Hide Caption 9 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – Known as "Lights Out" after knocking out four players in a high school game, Shawne Merriman entered the NFL with fanfare, earning 2005 Rookie of the Year honors. His 2006 suspension for steroid use prompted the "Merriman Rule," prohibiting any player who tests positive for steroids from going to the Pro Bowl that year. Hide Caption 10 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – After his former Texas Rangers teammate Jose Canseco accused him of using steroids, Rafael Palmeiro appeared before Congress to deny the allegations. Later that year, he was suspended from baseball for testing positive for steroids. He maintains to this day he has never knowingly taken performance enhancers. Hide Caption 11 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – Few NBA players have tested positive for steroids, not only because the sport relies less on raw strength and speed than other sports but also because the league didn't begin testing until 1999. Miami Heat forward Don MacLean became the first to fail a test in 2000, and he was suspended for five games. Hide Caption 12 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – After racking up awards in college football, Ricky Williams was picked in the first round of the pro football draft in 1999. After testing positive for marijuana in 2004 as a Miami Dolphin, Williams retired and studied holistic medicine in California. He returned to the Dolphins the following year, only to have more run-ins with the NFL drug policy. He retired again in 2011. Hide Caption 13 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – Bill Romanowski was known for hard hits on the gridiron, but he also violently attacked teammate Marcus Williams during a scrimmage while playing for the Oakland Raiders. In a lawsuit, Williams blamed the attack on Romanowski's "roid rage." Romanowski settled the suit and in 2005 admitted to "60 Minutes" that he used steroids. Hide Caption 14 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – Sprinter Tim Montgomery set the world record in the 100-meter dash in 2002, but the time was scratched after he was found to have used performance-enhancing drugs. Since his retirement, he has had other legal troubles including arrests for money laundering and heroin offenses. He was sentenced to jail time for both. Hide Caption 15 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – An Olympian and renowned longball hitter, Mark McGwire spent his entire career with the Oakland A's and St. Louis Cardinals, breaking the single-season home run record in 1998. In 2010, he admitted using steroids over the course of a decade but told Bob Costas in an interview he took them only for health reasons. Hide Caption 16 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – Ross Rebagliati won a gold medal during the first year of snowboarding at the 1988 Olympics. He was stripped of the medal after testing positive for the active ingredient in marijuana. It became fodder for late-night talk show jokes, but Rebagliati eventually got his medal back after it was determined marijuana was not a banned substance. Hide Caption 17 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – A winner of eight Grand Slam events, Andre Agassi was considered one of the most dominant tennis players of the 1990s. In 2009, the tennis pro acknowledged in his autobiography that he had failed a drug test for methamphetamine in 1997 but skirted punishment by blaming an assistant. Hide Caption 18 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – Regarded as the best soccer player after Pele, Diego Maradona was known for his deft footwork and knack for finding the net. In 1991, he was suspended for 15 months after testing positive for cocaine. He would later admit he was addicted to the drug for about 20 years and began using when he was playing for Barcelona in the 1980s. Hide Caption 19 of 20 Photos: Photos: Drug scandals in sports Drug scandals in sports – A prolific sprinter in the 1980s, Canadian Ben Johnson routinely bested American Carl Lewis in the 100-meter dash. After winning the gold at Seoul in 1988, Johnson tested positive for a steroid. His coach said Johnson took the drugs to keep up with other athletes and later wrote a book saying all top athletes were using in those days. Hide Caption 20 of 20

Photos: Athletes and doping in the era of PEDs Photos: Athletes and doping in the era of PEDs Maria Sharapova, a five-time Grand Slam champion and the world's highest-paid female athlete, admitted that she failed a drug test at the Australian Open in January. She tested positive for meldonium, a recently banned substance that she said she had taken since 2006 for health issues. She will be provisionally banned by the International Tennis Federation on March 12. Click through the gallery to see other athletes accused of using drugs to boost their careers. Hide Caption 1 of 17 Photos: Athletes and doping in the era of PEDs In February, New York Mets pitcher Jenrry Mejia became the first player to be permanently suspended by Major League Baseball after he tested positive for a performance-enhancing substance. MLB said Mejia tested positive for boldenone, an anabolic steroid that athletes use to increase muscle mass. Hide Caption 2 of 17 Photos: Athletes and doping in the era of PEDs New York Yankees slugger Alex Rodriguez confessed to using performance-enhancing drugs in a meeting with the Drug Enforcement Administration in January 2014. Rodriguez told DEA investigators that he had used banned substances, including testosterone cream, testosterone gummies, and human growth hormone, between late 2010 and October 2012. He was suspended for the entire 2014 season. Hide Caption 3 of 17 Photos: Athletes and doping in the era of PEDs Olympic sprinter Tyson Gay was banned for one year after he tested positive for a prohibited anabolic steroid in 2013. The four-time U.S. champion in the 100 meters received a reduced punishment from the two-year suspension standard for cooperating with authorities. The 4x100 relay team he was on was stripped of the silver medal it won in the 2012 Olympics. Gay returned to racing in 2014. Hide Caption 4 of 17 Photos: Athletes and doping in the era of PEDs Ryan Braun of the Milwaukee Brewers admitted to using performance-enhancing drugs in 2011, the year he was National League MVP. He said he took a cream and a lozenge with banned substances while recovering from an injury. Hide Caption 5 of 17 Photos: Athletes and doping in the era of PEDs In 2013, Lance Armstrong admitted to doping throughout his cycling career. The seven-time Tour de France champion confessed to using testosterone, human growth hormone and blood transfusions to enhance his performance. Hide Caption 6 of 17 Photos: Athletes and doping in the era of PEDs Mixed martial arts fighter Alistair Overeem failed a random drug test in 2012 and admitted to injecting himself with a substance that contained testosterone, prescribed for a rib injury. He was suspended for nine months. Hide Caption 7 of 17 Photos: Athletes and doping in the era of PEDs Barry Bonds, baseball's all-time home run leader, was convicted of an obstruction charge in 2011 after he impeded a grand jury investigating the use of performance-enhancing drugs. Bonds had testified that he thought his personal trainer was giving him arthritis balm and flaxseed oil, not steroids or testosterone. Hide Caption 8 of 17 Photos: Athletes and doping in the era of PEDs Houston Texans linebacker Brian Cushing was suspended for four games after testing positive for a drug called human chorionic gonadotropin in 2010. Hide Caption 9 of 17 Photos: Athletes and doping in the era of PEDs Cyclist Floyd Landis admitted in 2010 to using performance-enhancing drugs for most of his career. Landis used the red-blood-cell booster erythropoietin, known as EPO, along with testosterone, human growth hormone and frequent blood transfusions. He was stripped of his 2006 Tour de France win and suspended from cycling for two years. Hide Caption 10 of 17 Photos: Athletes and doping in the era of PEDs In 2008, Olympic track star Marion Jones was sentenced to six months in prison for lying to federal prosecutors investigating the use of performance-enhancing substances. Hide Caption 11 of 17 Photos: Athletes and doping in the era of PEDs Former New Orleans Saints defensive lineman Charles Grant tested positive for banned substances in 2008 and was suspended for the rest of the season. Hide Caption 12 of 17 Photos: Athletes and doping in the era of PEDs Retired New Orleans Saints running back Deuce McAllister tested positive for a banned diuretic in 2008. Hide Caption 13 of 17 Photos: Athletes and doping in the era of PEDs Shawne Merriman, then of the San Diego Chargers, was suspended for four games after testing positive for steroids in 2006. He retired in 2013 after eight NFL seasons. Hide Caption 14 of 17 Photos: Athletes and doping in the era of PEDs Baseball slugger Mark McGwire evaded questions about steroid use when speaking to Congress in 2005. But in 2010, he admitted that he had used steroids during the 1990s. Hide Caption 15 of 17 Photos: Athletes and doping in the era of PEDs Home-run hitter Sammy Sosa was among the players who tested positive for performance-enhancing drugs in 2003, according to the New York Times. Hide Caption 16 of 17 Photos: Athletes and doping in the era of PEDs Former NFL linebacker Bill Romanowski appeared on "60 Minutes" in 2005 and admitted to using steroids and human growth hormone during his career. Hide Caption 17 of 17

The league may seek to ban the players for 100 games by counting the doping itself as one infraction and lying about having taken the drugs as a second one, ESPN reported. Major league players can appeal any possible suspensions, as Braun did in 2012.

That year, a drug test showed high levels of testosterone in his body, but the outfielder successfully disputed the testing process , and the suspension was overturned in February.

Asked about the ESPN report Tuesday, Braun said he was sticking by his previous account. "The truth has not changed," he told reporters, declining to comment further.

CNN has not independently confirmed the ESPN report.

A Florida newspaper first leveled doping allegations at Rodriguez in January. The Miami New Times reported that the shortstop and third baseman had acquired the drugs from a now-closed Miami anti-aging clinic called "Biogenesis," run by Anthony Bosch.

ESPN said Bosch, who allegedly supplied baseball players with performance-enhancing substances, has agreed to cooperate in the MLB investigation. CBS Sports also confirmed Bosch will talk to investigators.

Records obtained by MLB name many players, but league investigators need Bosch to attest to their accuracy and confirm that players were doping, ESPN reported, citing unnamed sources.

The league filed a suit against Biogenesis in March for allegedly supplying PEDs to players and advising them on how to avoid detection during drug tests.

ESPN reported that MLB may drop the suit against Bosch, if he cooperates in its investigation.

Managers tight-lipped

On Tuesday, the managers for the Yankees and the Brewers said little.

"I know Major League Baseball is handling it, and that's all I know," Brewers manager Ron Roenicke told journalists at a post-game news conference in Milwaukee.

Yankees manager Joe Girardi started out dodging reporters who grilled him on ESPN's report after New York's game but softened when it came to his concerns about Rodriguez.

"I always worry about my players, always," he said. "One thing you never want to forget is -- they're human beings."

He did not say whether he had discussed the looming scandal with Rodriguez.

"When I talk to Alex, it's baseball-related. That's what it is," Girardi said.

He feared the game he has dedicated his life to will suffer because of the scandal.

"I worry about baseball being affected as a game, the whole thing, and what it's been through in the last 15 years."

Rodriguez was at the Yankees training facility in Florida on Tuesday, recovering from an injury. He could not be reached for comment. A 100-game suspension could cost him more that $15 million, ESPN reported.

New York outfielder Vernon Wells was discouraged by the scandal.

"We've done so much as a group to try to rid ourselves of conversations like this," he said.

In spite of advances in drug testing, new doping techniques designed to avoid detection keep coming, Wells said.

"There's always someone out there trying to beat the system from a medical standpoint."