For many, the US Open marks the fourth and final time that attention must be paid to tennis for the year. From a historical standpoint, that's an accurate assessment. Little to nothing that happens for the rest of 2013 will be remembered in the long run. The No. 1 rankings on both tours have been decided, Masters events feel a little smaller when they don't lead to a major and Andy Murray announced that he's going to have back surgery and likely won't be seen again until 2014.
Yet tennis will be played, by the rest of the best in the world, and sometimes what happens in the fall doesn't just stay in the fall. Two years ago, Roger Federer began his long run back to No. 1 with three late-season tournament wins. Here are four things to keep an eye on over the last six weeks of 2013.
Can Novak Djokovic adjust?
Your move, Nole.
With his US Open win, Rafael Nadal has not only won his past three matches over Djokovic, he has taken his No. 1 ranking, as well. This is one of the few rivalries that really has gone back and forth. After losing seven straight to Djokovic, Nadal brought more aggression and variety to their matches.
What can the Serb do to counteract that? In the past, he was patient against Rafa, but to play that way you have to be confident that you can win in the end. The indoor hard-court season, where Rafa traditionally struggles, should offer Djokovic a few chances to get that confidence back going into 2014.
Can Rafa sustain?
Even in Nadal's No. 1 seasons, 2008 and 2010, he faded down the indoor stretch. He has never won Shanghai, Paris or the World Tour Finals -- the latter is the only event of real significance missing from his resume. The faster surfaces and faster play indoors hurts Rafa, as does his body, which is typically beat up by the end of the season.
He says he'll try to do better this time, though it would also make sense for him to rest his knees at this time of year. Will Nadal continue to have highs and lows in his late 20s? Or will he be a consistent No. 1? We'll get an early answer this fall.
Can Roger bounce back?
As I said above, this has often been a time for Roger Federer to shine. He has won six World Tour Finals, and he loves indoor hard courts the same way Rafa loves outdoor clay.
When we last saw him, at the US Open, the 32-year-old Federer's expectations appeared distinctly lowered -- after months of back trouble, he just wanted to be able to train well again. This fall will tell us how that's going. If he can win a title, make himself competitive and qualify for the WTFs, he'll feel better for 2014. But more early losses would, like the early losses at the majors this year, be something new -- Federer has always finished strong.
Is anyone in the same league as Serena?
For most of the past two seasons, the WTA had a healthy and competitive big three -- Serena Williams, Victoria Azarenka and Maria Sharapova divvied up the big titles, played often-intriguing matches and were virtually always in contention.
Now that ruling class is on shakier ground, yet no one has risen up this year to challenge them, either. Sharapova, after shoulder problems and a lost summer with Jimmy Connors, has fallen off, while Vika failed to close the gap with Serena at the Open.
It feels again as if there's Serena ... and everyone else, and this fall will be a battle to see who's the best among everyone else. The one must-watch will be the tour championships, which are in Istanbul for the last time. Will Sharapova be there? Can Vika regain her momentum? Or will Serena, at 32, finish what might be her best season yet?