With money for professional athletes at unprecedented heights, there has never been more temptation to cheat. Somewhere, as we speak, there is probably a cutting-edge chemist/doctor manipulating compounds, looking for a way to beat the dope-testing system.

The recent news has been depressing:

Milwaukee Brewers left fielder Ryan Braun was suspended 65 games for use of performance-enhancing drugs. And the next Biogenesis wave threatens to engulf a host of All-Star-quality players, from Alex Rodriguez to Nelson Cruz.

It's the same in the NFL, where five players were suspended in July alone for violating the league's substance abuse policy, including Denver Broncos linebacker Von Miller.

American sprinter Tyson Gay won't be running in next month's world championships after reported multiple positive tests for an illegal substance, one at the nationals, where he won the 100- and 200-meter races.

Although this year's 100th Tour de France was widely believed to be the cleanest in the post-Lance Armstrong era, the sight of British cyclist Chris Froome charging up Mont Ventoux after 240 kilometers in the saddle inspired skepticism. Was he clean? "100 percent, 100 percent," the eventual champion answered after winning Stage 15.

Is it naïve to think that tennis -- a sport that requires extraordinary endurance and places unnatural physical demands on its most successful players -- is any different?

Yes.

After Armstrong admitted he had doped for years, 17-time Grand Slam singles champion Roger Federer used that precise word -- "naïve" -- in suggesting that tennis is tainted by cheaters just like every other sport. Rafael Nadal, for example, has never failed a drug test, but there have been repeated, random whispers that his 12 major titles were built on a foundation of better chemistry.

We may never know the truth, for the International Tennis Federation, the sport's governing body, has been criticized repeatedly -- even the French Senate's recent report weighed in -- for a weak, shoddy oversight system.

Perhaps that's why it was so startling when two former top-15 players were recently flagged for alleged doping transgressions. Serb Viktor Troicki was given an 18-month ban for failing to provide a blood sample at the April ATP World Tour event in Monte Carlo. Two days after that announcement, reports surfaced in the Croatian press that Marin Cilic failed a drug test that same month in Munich.

Naturally, both players are appealing and have detailed explanations. In doping there is always a story. Troicki, who did submit to urinalysis, claims the doctor said it was OK to pass on the blood test. The doctor says otherwise. Cilic wasn't notified of the positive test until before his second-round match at Wimbledon, then pulled out, citing a knee injury. His status, heading into the Montreal event, is unclear.

What is the incentive to dope? Follow the money.

Last year, Russian Mikhail Youzhny, now 31, finished as the ATP's No. 25-ranked player. He won 33 of 54 matches and won $879,840 in prize money. He undoubtedly collected much more through endorsements and off-the-record guarantees from smaller events. His counterpart among WTA players was Su-Wei Hsieh, a 27-year-old from Chinese Taipei who had never finished ranked higher than No. 79, but won two tiles and ended the year at No. 25. She earned an official $490,114 in prizes -- more than the president of the United States, minus book royalties, made.

This is not to suggest they are doping, but to underline the potential rewards of the sport.

Tennis has a history with drugs. In 1998, six months after he won his first (and only) Grand Slam singles title, Petr Korda tested positive for the banned steroid nandrolone. In 2010, Wayne Odesnik pleaded guilty to importing human growth hormone into Australia and was banned from tennis for one year. In between, there were more than two dozen verified episodes with illegal substances.

Back in May, Spanish doctor Eufemiano Fuentes was tried for supplying cyclists with blood transfusions. During the "Operation Puerto" trial, Fuentes admitted that also among his clients were soccer players, boxers and tennis players. He didn't name names and, conveniently, the judge in the case ordered that more than 200 bags of blood and plasma being held as evidence be destroyed.

Andy Murray, for one, was baffled.

"Puerto case is beyond a joke ... biggest cover-up in sports history?" he tweeted.

Fuentes got a year in jail. His unnamed clients got a reprieve when the evidence was destroyed.

The big four, including Nadal, have been pushing for stricter drug testing and more transparency in the process. They managed to push through some huge pay increases at the majors. The ITF would do well to listen to its leading players.

The last time we saw her on the major stage, Serena Williams was walking off the court after losing to German Sabine Lisicki in the fourth round at Wimbledon. Of course, a number of top-ranked players went home early from the All England Club.

Williams still has the best record in professional tennis so far this season, 51-3, which works out to a robust winning percentage of .944. She won all five of her matches at the event in Bastad, Sweden, although the highest-ranked opponent was No. 37 Klara Zakopalova, whom she beat in the semifinals.

Serena, who at 31 is the oldest woman to ever be ranked No. 1, is the top seed in next weeks Rogers Cup in Toronto. Two years ago, she was in a very different place, struggling to overcome a series of health scares. She won only two tournaments that year, at Stanford and Toronto, and that helped her find the confidence to put together the terrific run shes still on now.

Williams participated in a conference call with reporters Monday afternoon.

Q: How did you recover from that loss at Wimbledon?

A: Just training and practicing. I played a tournament in Sweden. You can't lick your wounds too long. There's always next week. I feel like I can fight for another week and another year.

Q: Do you still have drive to be the best women's player in history?

A: I don't really think about the history. I feel honored that it's even in the conversation. For me, the reason I started playing tennis wasn't to be the best player ever. It was to be the best Serena Williams can be. That has been my only goal. I definitely cherish each tournament more. When I was younger I definitely loved to win, but it's just a different time. I'm playing some of my best tennis.

Q: How are you a different player now?

A: Mentally, I'm a little more relaxed (laughs) even though it's hard to tell. It's been like that since there was a moment when I realized I might not be able to play again. Every match I've played since then I've appreciated it more.

Q: Is this the peak of your career?

A: I don't know even when I'll be able to answer that question. There's so much more I'd like to do, so many more tournaments I'd like to win. Personally, I don't think I have been [my best]. I feel like I've had a decent year for me. I would have liked to have done better at a couple of tournaments this year. I definitely want to get to the top of the mountain. If I'm there, I want to stay there.

Q: It's been a decade since an American man won a Grand Slam singles title. How do you explain that?

A: That's definitely surprising, especially with such great American men that we've had over the years, Pete Sampras, Jim Courier, Andre Agassi and Andy Roddick did a fabulous job of holding American tennis up there. I definitely didn't know that. I'm sure there's some American-made tennis players coming along. On the women's side, too. Not long ago, everybody was always asking me the opposite, when was someone going to win a Grand Slam? We'll definitely have a Grand Slam winner. Hopefully, it will be me.

Who's Hot

Williams

Serena Williams: 51-3 (.944)
Rafael Nadal: 43-3 (.935)
Victoria Azarenka: 28-3 (.903)
Andy Murray: 34-5 (.872)
Novak Djokovic: 39-6 (.867)
Maria Sharapova: 37-6 (.860)

Who's Not

Nadia Petrova: 9-12 (.429)
Janko Tipsarevic: 14-15 (.483)
Alexandr Dolgopolov: 15-16 (.484)

Ace leaders -- men

John Isner: 558
Kevin Anderson: 472
Nicolas Almagro: 470
Milos Raonic: 396
Benoit Paire: 384

Ace leaders -- women

Serena Williams: 323
Sabine Lisicki: 230
Maria Sharapova: 176
Kirsten Flipkens: 160
Petra Kvitova: 154

Federer

The appetizers have been served and now it's less than a month until the main meal of the summer.

Next week in Canada -- the men are in Montreal and the women in Toronto -- we'll see the first nearly full field since Wimbledon. All 15 of the top-ranked men are scheduled to play (No. 15 Marin Cilic, with his outstanding drug issue, may or may not take the court) and 12 of the top 15 women (Victoria Azarenka, Maria Sharapova and Marion Bartoli will return in two weeks in Cincinnati in advance of the US Open).

It should be an intriguing two weeks because New York will be the season's decisive major. Through three Grand Slams, we have six different singles champions. Someone (hello there, Novak and Serena) will have the chance to lock down player of the year honors

It feels like a return to 2000, when Andre Agassi, Gustavo Kuerten and Pete Sampras won the first three majors on the men's side, matched by Lindsay Davenport, Mary Pierce and Venus Williams. The winners at that US Open were ... an out-of-nowhere Marat Safin and an in-her-prime Venus.

Isner

Yes, the BB&T Atlanta Open featured the tallest final in ATP World Tour history. But 6-foot-10 John Isner's thrilling 6-7 (3), 7-6 (2), 7-6 (2) victory over the 6-8 Kevin Anderson was notable for another reason. It was the first time in more than 18 months that a men's final did not include at least one break of serve

In January 2012, Milos Raonic and Janko Tipsarevic played three breakers in Chennai with Raonic prevailing.

Isner hit 24 aces (and no double faults) in the 174-minute match, the longest ATP best-of-three final this year. He saved 11 break points with some phenomenal serving. Facing the first of two match points, Isner cracked a 143 mph ace. His last serve of the match was clocked at 146.

The former Georgia Bulldog won a "home" title, the seventh of his career. Three of those came when he saved a match point and won a third-set tiebreaker. Isner, up two spots to No. 20, is 8-0 in decisive-set tiebreaker matches over the past two years.

Cibulkova

After losing in the second round at Roland Garros -- where she was a semifinalist in 2009 -- Dominika Cibulkova found herself with a 13-14 record at the end of the clay-court season.

Now, after two grass events and the hard courts of the Bank of the West Classic at Stanford, the fiery Slovakian has won eight of 10 matches and is now 21-16. Cibulkova beat top-seeded Agnieszka Radwanska in a three-set final, which was surprising considering she didn't win a single game in their previous match in Sydney.

Cibulkova, at 5-foot-3, is the shortest player in the WTA's top 25.

Fognini

The sweet run of Fabio Fognini continues.

The 26-year-old Italian reached his third straight final, at the Vegeta Croatia Open in Umag. After winning the titles in Stuttgart and Hamburg, Fognini fell to Tommy Robredo 6-0, 6-3.

"It was an incredible week," Fognini said afterward. "I go home with a lot of happiness. I'm a little bit disappointed, but even if you're Roger or Rafa, you're going to lose sometime. I've played three incredible weeks and they're going to stay in my head for the rest of my life."

Fognini's win streak ended at 13, the fourth longest of the ATP season. He is now ranked a career-high No. 16. He's the first player since Juan Martin del Potro (2008) to win the first two titles of his career in back-to-back weeks.

Robredo, 31, is also enjoying a terrific summer. Once a top-five player, the Spaniard started the year at No. 114. Now, he's back in the top 25. Thirteen ATP titles have been won this season by players aged 30 or over, matching last year's total with three months left to play.

The USTA announced Wednesday that the upcoming US Open will be the richest tennis tournament in history, with prize money of $34.3 million all told.

The men's and women's champions will each receive $2.6 million, an increase of 37 percent and about $150,000 more than the winners received at Wimbledon. Finalists are guaranteed $1.3 million with semifinalists at $650,000. First-round losers will earn $32,000, with those advancing to the second round getting $53,000.