After the revelation of Lance Armstrong's systematic doping offered yet one more example of widespread performance-enhancing-drug use in professional cycling, another popular international endurance sport is under heavy scrutiny: Tennis.

Roger Federer, the all-time leader in Grand Slam titles, is among the world's top players calling for improved screening methods.

"We don't do a lot of blood testing during the year," Federer said at the final event of the men's pro season. "I'm OK with having more of that. I just think it's important to have enough tests out there. I think it's key and vital that the sport stays clean. We have a good history in terms of that and we want to make sure that it stays that way."

Andy Murray, the 2012 U.S. Open champion, agreed, saying, "We do a fair amount of drug testing, but we could do more. A lot of it has been urine, not so many blood tests. I think tennis is a clean sport, but the more we can do to prove that all the time is good."

What makes these comments all the more interesting is that top stars from the previous generation, including Jim Courier, Andre Agassi and Todd Martin, are also pushing for more aggressive testing for PEDs.

"I love to hear that some of the world's best are calling for more," said Martin, a two-time Grand Slam finalist, a recent masters event in San Jose. "I think that at this point in time, it's the only way to begin to cut that gap down between the science of cheaters and the science of testing, and even then, I don't know how much it's going to be able to be caught up with."

That's why many are concerned that the International Tennis Federation's anti-doping program has come in under budget for three consecutive years, according to documents released by the sport's world governing body. The amount of tests it is conducting is actually going down, which led Federer to make his early-November comments. He said the number of times he has been tested in the past six to eight years has decreased, when he believes the opposite should be happening.

"I know I got tested one year eight times blood, 20 times urine, three out-of-competition, unannounced at my front door" said Agassi, who was ranked No. 1 as late as September 2003 and retired after the 2006 season. "So I thought that was pretty aggressive, but I would have been fine with it had it been more. But I think less is a problem."

According to the ATP, tennis became the first professional sport to institute a practical drug-testing program, in 1985. Out-of-competition testing -- versus solely unannounced screening at certain tournaments -- was considered as early as 1992, but not fully implemented until 2005 and not mandatory until 2009. Today, players must provide their daily whereabouts to the organization to allow for testing without notice, but the decrease in frequency is an issue.

Agassi, an eight-time Grand Slam winner, admitted in his 2009 autobiography "Open" to being caught for using crystal meth in 1997 through a urine test. He explained in the book that he wrote a letter to the ATP falsely denying the positive test. He was spared the public damage this revelation would have had on his career, as well as a three-month suspension for recreational drug use.

While Agassi hadn't taken a PED, John McEnroe, who won seven Grand Slam singles titles, acknowledged in 2004 that for six years during his career he unknowingly ingested steroids.

"People have to become more aware of what they putting into their bodies," McEnroe told a British newspaper at the time. "In general people are administered drugs too readily."

Now, the restrictions are accepted as being tighter.

"It’s a short leash, and it’s year-round sport," said Agassi of the current standards. "I think it’s great to have that kind of oversight, because it assures fans that if there [is] anybody that cheats, the sport itself will expose that, because you can’t get away with that under these strict rules forever. Maybe you can get lucky once or twice, I suppose, but the governance is what I look at, and I think our sport has been on the front line and set the bar for accountability. Whatever the players can do to assure the fans that what they're doing is a function of their talent and hard work, absolutely."

But is it enough?

Victor Conte (pictured below), founder of the defunct Bay Area Laboratory Co-operative (BALCO), tweeted earlier this month that PED use in tennis is "likely rampant because testing is inept." (Conte served four months in prison after the federal investigation that linked high-profile athletes such as Bill Romanowski, Marion Jones and Barry Bonds to banned substances.)

Courier, a four-time Grand Slam champion, spoke out about his perception of increased PED use in the sport shortly before retiring in 2000, and he hasn't changed his mind.

"What I was vocal about at the end of my career," said Courier in San Jose, "was that there were certain things that they just didn't have the capacity to test for. They weren't testing for certain things that were the most important areas that people could get ahead, and I don't know if they're testing for those things now."

The drugs Courier alluded to then were erythropoietin, or EPO, and growth hormones, commonly referred to as HGH. EPO use increases the red blood cell count, providing more oxygen to the body, which increases an athlete's endurance. Growth hormones stimulate the regeneration of cells, and are generally associated with recovering from injuries faster. Since the early 2000s, both have been detectable through testing. EPO can found in blood and urine. But the subtleties of naturally occurring HGH versus the artificial kind can only be deciphered through blood tests.

In 1998, shortly before Courier called attention to what he believed was this growing problem in tennis, Czech player Petr Korda was popped for using an anabolic steroid. He a failed test after losing in the quarters at Wimbledon. Korda had won the Australian Open just months earlier, but was not stripped of the title. Nor was he subsequently punished with, at that time, the minimum one-year suspension after stating he never knowingly used the performance enhancer. Korda only had to surrender his winnings and ATP points from Wimbledon.

In a similar case, British player Greg Rusedski was suspected of doping after a test in July 2003 came back showing the same steroid Korda had used, nandrolone. Rusedski peaked in the world rankings at No. 4 after losing in the 1997 U.S. Open finals. By the time his tests were called into question in 2003, Rusedski had fallen to No. 70.

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Just before Rusedski's flunked test, seven other players -- of which only Czech Bohdan Ulihrach was ever named -- were alleged to have used the same steroid. Each was pardoned after the ATP chose not to contest the group's claim that a tainted supplement distributed by sanctioned tournament trainers was responsible for the positive tests, despite later analysis showing otherwise. Summoning the same defense as these other players, Rusedski appealed and was cleared to resume his career. He climbed back into the top 40 in 2005, before retiring in April 2007 at age 33.

Such rules and occurrences are not reserved just for the men, but to the women also, who play under the umbrella of the WTA. In December 1997, American teenager Samantha Reeves was found guilty of having nandrolone in her system, but was let off the hook because, per the ITF Appeals Committee's statement, she was "naïve and immature at the time of the offense."

Regulations on PEDs have been in place for years. There's a two-year ban for the first positive test and a possible career-ending suspension for a second. But these examples show they are stripped of their teeth if there is ultimately no real enforcement.

"The sport is no different than insider trading or Ponzi schemes," Martin said. "There are people out there who don't have the ethics that are necessary for there to be a level playing field, and as long as there are, we're going to have those who are trying to get a leg up."

Martin also said the way the tests are evaluated should be modified to gauge differences in an individual's results.

"Guys need to be tested against themselves, as opposed to being tested against the standards," he said. "I think we all have standards within a certain range, but if we can identify really well what everybody's benchmarks are, then I think it's easier to [notice] minor changes."

Courier concedes that even if better testing and enforcement created stronger deterrents, it wouldn't eliminate the temptation.

"Let's face it, if you're 100 in the world and you think that something illegal will get you to 10 in the world, that's a tremendous difference in the quality of the rest of your life from a financial standpoint," said Courier, the U.S. Davis Cup team captain since October 2010. " ... You're never going to wipe out the human nature, the human desire to get ahead by bending corners. Everywhere you look, where there are gains to be made, people do it."

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