There has been some fruitful tennis played this year, which resulted from an immense improvement from certain players like Andy Murray.
However, whenever there is improvement, there is always a small key group who will face regression, and sometimes it will linger—impeding on their goals.
This year, a number of highly-ranked players fitted into this category and showed us that nothing lasts forever.
These are my top five tennis players who are regressing instead of getting better.
Despite her clean sweep so far during the Rogers Cup, it is no secret that Caroline Wozniacki is a player in regress.
Wozniacki has created her own personal record. Although she was ranked No. 1 by the WTA for two consecutive years, she came away empty-handed in the Grand Slams despite her flawless rankings.
That alone tells us that it may not be Wozniacki's game that is letting her down, but maybe she does not have what it takes to win.
Maybe Wozniacki is not ambitious enough to win, or maybe she is content with being in the top 10 and does not have a burning desire to go for the W.
At the moment, Wozniacki is ranked No. 8, a far cry from her rankings in the past two years, and a major fall from grace.
The reason that the Dane's ranking has dropped so low could be analyzed for hours without an intelligible and precise answer, but there is no point in fixing a game that has no screws loose.
America's tennis has plummeted recently, especially on the men's side.
Andy Roddick was disconnected from the Top 10 in the rankings in 2011 after nine straight inclusive years. This year, Roddick is ranked No. 21, a shocking statistic for the man who has carried America's tennis success on his shoulders since he turned pro in the year 2000.
The question of Roddick retiring is one to which every A-Rod fan wants an answer, but the answer is unlikely to come from Roddick himself.
Roddick's demeanor has changed recently. He lacks motivation, and his tennis has faltered dramatically. Roddick also missed the majority of the clay season, only opting to play tournaments he enjoys the most.
This has left his fans suspicious, and wondering if Roddick is creating a mental scrapbook of his last memories every time he exits a tournament.
Injury and illness have certainly taken their toll on Venus Williams, as she was ranked outside the Top 100 in 2011, and became unranked for the first time in 15 years.
Although she improved her ranking in 2012, Venus' tennis has been inconsistent thus far this year. There were glimpses of the old Venus during Charleston and Rome, where she made the quarterfinals after a drought of play. She had her work cut out for her to make a comeback.
Venus' efforts came to a halt during Wimbledon, when she was beaten in the first round by Elena Vesnina in straight sets, but this did not discourage the American veteran, as she returned to the Wimbledon courts for the Olympics, but had to walk off the courts prematurely when she was beaten by Angelique Kerber in the third round.
Although Venus had success when paired with her superstar sister, who is in flying form, it is questionable whether Venus will actualize her potential and become a queen of women's tennis alongside her sister again.
Regression happens to the greatest of champions, and because we forget that Roger Federer is only human, sometimes we become startled when we notice his weaknesses.
Signs are beginning to show that Federer, the king of the courts, has started to slow down. There is no shame in Federer's regression.
Even with his regression apparent, Federer can still win Grand Slams and can still play flawlessly functional tennis. However, the difference between now and his heyday, which would be arguably between 2006 and 2007, is that there are some spots of weakness in his game which can be attacked.
We saw this when Murray demolished him, preying upon his weaknesses at the Olympics. The old Federer would have clinched the break points and put up a fight, but at the age of 31, Federer is not getting any younger and looked a little sluggish playing against Murray at the London Games.
It will be interesting to see whether Federer will be undercut by his younger counterparts like Murray and Nadal, or whether he can cut back on the copious number of errors he made in his game at the Olympics and come back fighting.
Something will have to change if John Isner, the highest-ranked American player, is ever going to win a Grand Slam.
Although Isner reached his career-high singles ranking this year, he did not play with poise in certain matches, and he did not look like someone who was trying to win or even had a desire to win.
During his game at the French Open against Paul-Henri Mathieu, Isner looked lost. He had no confidence after a one-month streak of sluggish tennis performances, and at certain points in the match, Isner just watched balls pass by him with no response.
His blazing serve is his strength, but at 6'9" and 245 Ibs, Isner has an inability to get down low and is not extremely agile or quick-footed, which rules him out of playing at a high level on grass.
Isner really needs to play with conviction if he is to move forward, crack the Top Five and mix with the top-ranked players in the game.