It's been an unpredictable year in tennis, with surprise winners, breakthrough players and familiar faces making a comeback. So what's in store as the season wraps up? Here's what to look for as the tours wind through Asia and the European indoor events.
1. The state of the Big Four
The most noticeable shifting in the tennis landscape this season has been the reduced dominance of the Big Four of Roger Federer, Rafael Nadal, Novak Djokovic and Andy Murray, who came in having won 34 of 35 Grand Slams. But this year, they have captured only two among them, with injuries, age and off-court priorities affecting their form and performance. That means each will want a good showing during the next two months. Murray has taken wild cards into two extra events before the Shanghai Masters, still looking for his best tennis following back surgery. Apart from grass, Federer is now at his strongest indoors and has typically done well at the Paris Masters and Tour Finals following the Asian events. And Djokovic, who dominated this portion of the season a year ago, has a lot to defend as he attempts to stay at No. 1.
2. The Rafa watch
It is Nadal's return that be might be the most interesting to watch, with a wrist injury keeping the Spaniard sidelined since his fourth-round defeat at Wimbledon. He will play an exhibition before beginning his first tournament in Beijing and has traditionally not done well during this portion of the season. This time, he is in an unusual position -- not as tired as usual but lacking match practice. As such, it's hard to tell how he might do, especially since conditions at these events do not suit his game.
3. Backing up breakthroughs
Even before the US Open, the season had seen several players make Grand Slam breakthroughs. There was the Australian Open victory by Stan Wawrinka and the French Open semifinal appearance by Ernests Gulbis. Then Milos Raonic and Grigor Dimitrov reached the Wimbledon semifinals. Generally, however, they have not yet followed up on those performances. Even Wawrinka, who won Monte Carlo and got to the Wimbledon semifinals, has had a very uneven season. Will US Open champ Marin Cilic and finalist Kei Nishikori do any better? Nishikori will make his return at some familiar locations in Southeast Asia, where he received so much attention for his US Open exploits, while Cilic has done well on hard courts this season, and his game should be suited to the speed of the courts in Asia and indoors.
4. Serena showing up
Serena Williams' commitment to the post-Slam events has been intermittent at best, and her desire could be questionable following her US Open victory. But she did show up in 2013 to win Beijing and the WTA Championships and has said she is planning to play in China. If she does, she will again be the favorite, and it will mark the second straight year she has been No. 1 and played a full season. At 32, it's no small achievement, especially given how infrequently she has done it during her career.
5. Li's status
This season marks the WTA's big shift into Asia and especially China, and the WTA championships will be played in Singapore for the first time. Li Na is a big reason the sport's profile has grown so much in the region, and she will be front and center for this stretch of events, starting with her new hometown tournament next week. But there has also been speculation about whether the 32-year-old might then decide to retire. Sidelined since Wimbledon with a knee injury and having ended her coaching relationship with Carlos Rodriguez, she is a big question mark despite her Australian Open victory to start the season.
6. Challengers for Serena
Even though Williams has not been as dominant this year, rivals like Maria Sharapova and Victoria Azarenka have seen an even bigger drop-off in their performances, increasing the gap between the world No. 1 and the field. There is no shortage of contenders to establish themselves behind Williams -- from former No. 1s like Sharapova, Azarenka, Ana Ivanovic and Caroline Wozniacki, to occasional big title winners like Petra Kvitova and Agnieszka Radwanska, to emerging players like Eugenie Bouchard and Simona Halep. But no one is doing it at the moment, so the next few events could be an opportunity.
7. Older women
New names like Bouchard have received plenty of attention this year, but some of the best stories have been the renewed successes of once-familiar names. The final in Quebec City this weekend was a perfect example, with 32-year-old Mirjana Lucic-Baroni winning her first title in 16 years by defeating 34-year-old Venus Williams, who has returned to the top 20. In an even older matchup, Venus took on 43-year-old Kimiko Date-Krumm in the first round of the US Open. Two 32-year-olds, Serena and Li, also won Grand Slams this season. That could inspire a few more veterans to recapture their form.
8. Younger men
Veterans have been the story on the men's side for a while, but a few teenagers have started to make their way on the ATP tour once again, starting with Nick Kyrgios. The Australian 19-year-old defeated Nadal at Wimbledon and has produced some good wins since. His challenge now is to keep it going as other players become more familiar with his game. Others like now-20-year-old Dominic Thiem and teens Alexander Zverev and Borna Coric have also grabbed attention, and their progress is something to watch.
9. Davis Cup
The return of Roger Federer has added excitement to what might otherwise have been an unusually lackluster year for the team competition. With Wawrinka now also a top-five player, Switzerland will go for its first Davis Cup title against a deep French team, and Federer will be looking to add the one significant victory he has not yet put on his résumé. For the French team led by Jo-Wilfried Tsonga, Richard Gasquet and Gael Monfils, it is an opportunity to make up for its Grand Slam frustrations in front of a home crowd that values Davis Cup and is expected to pack the stadium for the tie. It should be a memorable one.
10. Offseason exhibitions
The offseason break will feature plenty of tennis this year, with the usual exhibitions and the beginning of the International Tennis Premier League (ITPL) being played in various Asian cities. A lot of big names, including Djokovic, Nadal, Murray and Serena, are scheduled to play in the league, where teams of ATP, WTA and retired players will compete against one another. The most significant thing might be how this will affect the players going forward. Both Djokovic and Nadal played heavy exhibition schedules a year ago and had some uneven performances and injuries at the beginning of this season.