Little time for Serena Williams to waste at this point in her career

— -- Serena Williams takes tennis to places it has never gone before, but she turns 34 on Saturday, and that raises the question: Where will tennis now take Serena Williams?

Just last week, Williams made headlines after she appeared in Pirelli's annual celebrity-laden calendar, which is so exclusive that nobody can buy it. (You can, however, purchase the company's tires.) Serena also appeared on various news feeds for matters such as the "are they or aren't they" relationship with rapper Drake as well as another foray into fashion with HSN.

Tennis? Oh, there is that, too. Williams almost had a season Grand Slam. She didn't get it. Clearly, she's moved on. But we've been here before, and that -- combined with Williams' age -- adds urgency to the issue of where she goes from here.

Back at the tail end of 2003 and the beginning of 2004, on the heels of completing her "Serena Slam," she seemed bent on forging a new career. She wanted to become an actress but learned the hard way that she was no thespian and that her tennis résumé wasn't going to get her anything but an occasional cameo.

Williams got over that phase and rediscovered her drive as a tennis player. She went on to become, arguably, the greatest woman's player of all time. And this year, she almost ended that debate for good by sweeping all four majors.

But Williams failed. And the way she failed, writhing and struggling before our eyes -- despite persistently denying she felt any pressure -- revealed the nature of this unique beast, the Grand Slam. It also made us realize just how fiercely Williams wants to maintain her reputation as a fearless competitor.

Despite the missed opportunity, Serena is up at another level once again. But this time, she's not a 22-year-old with a wide-open future. The toxic celebrities have all been flocking to her again, anxious to be affiliated, to be part of what's happening. That's probably not great news for Williams, because she doesn't have a lot of time to waste.

Back at Wimbledon, Serena's coach, Patrick Mouratoglou, tried hard to tone down all the season Slam hype. He said that challenge was much like the mission to tie and ultimately surpass Steffi Graf on the all-time list of Grand Slam singles title holders. (Graf has 22, Serena 21.) There was nothing do-or-die about it.

"If she gets [the Grand Slam], it will be great," Mouratoglou told before the US Open. "But she doesn't need to put pressure on herself. If she doesn't get No. 22 at the US Open, she has the next year, and after that."

It was wise of Mouratoglou to subtly shift the emphasis to the task of surpassing Graf's title count, which, at this point, is a more realistic goal. But as formidable as Serena is, that may not be the slam dunk it appears, either. For great players of either sex tend to win Grand Slam titles -- until they don't.

Roger Federer is the same age as Serena. He won majors left and right until he hit a wall after winning his 16th at the Australian Open of 2010. Since then, he's won just one. Pete Sampras went two years without a major title until he went out in a blaze of glory by winning the US Open of 2002. And he was just 31 at the time.

OK, those are men. So take Chris Evert. She won her last major at the French Open of 1986 at the age of 31. She played for 3½ more years and never won another big title. Martina Navratilova, Evert's nemesis, won Wimbledon in 1990 (age 33) -- and failed to win another major singles title in more than four more years of competition.

The message in the careers of most great players? All good things come to an end. Quicker than you may think.

In 2015, Williams was living on a wing (her ace-making right arm) and a prayer, escaping one close call after another. (She played 18 three-set matches and lost the first set in 13 of them.) Her opponents still know that even when she's struggling, Williams can lift her game to new heights and crush them with impunity. But they also know she's human, and susceptible to pressure. The young ones, in particular, will feed on that.

Williams also may feel, understandably, like she's earned a rest. But she can ill afford one at this stage, if she wants to catch and surpass Graf.

The good news for Williams? Graf was one of the few great players who ended her career with a Grand Slam bang when she won the French Open at the age of 30 in 1999.

Two titles for Williams in 2016 would wipe out any bitter aftertaste from this year's US Open, and thus end her quest to become the greatest champion of the Open era.