A-game too much to ask before U.S. Open

We all saw Roger Federer struggle mightily to overcome David Ferrer on Thursday in Cincinnati (it went 6-4 in the third), despite the world No. 1 having owned the Spanish grinder since forever. It was a pretty apt symbol for the state of tennis these days, as well as a broader comment on the changing nature of the summer hard-court circuit -- or, as the United State Tennis Association prefers to call it, the U.S. Open Series.

Federer is still futzing with the Greatest of All Time crown that sits on his head (you know how Roger is about his hair), and making funny goo-goo daddy faces at his newborn twins; Rafael Nadal is testing his knees as carefully as a once-frisky senior citizen might adjust to a replacement hip; Novak Djokovic is treading water (this has been his modus operandi for months now). Granted, Andy Murray seems fully focused on the tasks at hand, but don't you sense that the "other Andy" basically got answers to whatever questions he might have had after absorbing that devastating Wimbledon loss?

The game is an unstable chemical compound these days, and it's even more pronounced on the WTA side of the fence. We saw how Venus and Serena Williams were both upset one tournament ago in Cincinnati; this week Dinara Safina and Venus Williams both blew up in Toronto as the tournament was barely under way.

You can chalk some of this up as luck-of-the-draw, that's-why-they-play-the-game, on-any-given-day stuff, and it's also true that we may have passed the tipping point when it comes to depth at the top of either game. But there may be something else going on, and it just might add to the mounting challenges for the U.S. game.

Simply put, the U.S. Open Series -- a terrific idea all around -- is having trouble sustaining the kind of traction that the bigwigs at the USTA anticipated. On paper, the idea was and remains terrific: link up all the North American tournaments that take place in a compressed, orderly fashion leading up to the U.S. Open; give the players a huge financial incentive (try doubled prize money) to win the Series.

Ironically, a model for this kind of "mini circuit" existed before the U.S. Open Series was spawned, in the form of a string of clay-court tournaments that lead up to the French Open. (It's a "French Open Series" in all but name.) But there's a critical difference between the tournaments preceding the second and fourth Grand Slam events: Heading for Paris, the players are relatively fresh and they know what's at stake -- a one-month period when the French Open and Wimbledon play a disproportionate role in making or breaking a year.

It's different in July and August, the home stretch of what most sports fans think of as "tennis season." And more and more for the top stars, the summer hard-court circuit is about maintaining, rather than achieving; it's about keeping your powder dry for the last big battle of the summer. You can't blame the players for this; they're just following the natural rhythm of the year and the demands of the preeminent majors.

Murray may yet underscore the credibility and value of the U.S. Open Series, or perhaps Federer will -- should he hang on in Cincy this week and rock the house in New York. But by this time of year, most of the players are too fatigued and too focused on one final push in New York to feel obliged to find their A-games for the U.S. Open Series events, even if they are WTA Premium or ATP Masters 1000 meetings.

This isn't the worst thing; the unpredictability of the hard-court season keeps us interested in a one-eyed kind of way, and it enhances the storylines emerging for the U.S. Open. The last thing you'd want in New York is for a Federer or Williams to admit that he or she left her best game back on the trail, in Montreal or Washington.

More and more, it's clear that the only tournaments that really matter are the majors. And it's never more valid than at this time of year.