With US Open Looming, the Window's Closing for Anyone to Catch Serena Williams

Angelique Kerber came within one match of ending Serena Williams' streak of 183 consecutive weeks at No. 1. It may have been Kerber's best chance to overtake Williams this season. The U.S. Open could be the last chance. 

Karolina Pliskova defeated Kerber 6-3, 6-1 to win the Western & Southern Open in Cincinnati on Sunday. The loss leaves Kerber 190 points behind Williams, who withdrew from the tournament, citing a shoulder injury. Williams leads Kerber by 480 points in this year's points race. 

Whether Kerber choked, was too tired or simply outplayed is irrelevant to the missed opportunity and narrowing window on the race for No. 1. 

If No. 2 Kerber or No. 3 Garbine Muguruza fail to dethrone Williams at the U.S. Open, they might as well move that goal to the top of the 2017 to-do list. 

If Williams wins there, she'll have no points to defend for the rest of the season. Remember, after her painful loss to Roberta Vinci in the 2015 U.S. Open semifinal, Williams shut down the rest of her season.

In doing so, she forfeited a ton of points, especially at the year-end WTA championships. 

This year, Williams withdrew from the Madrid Open, Rogers Cup and Cincinnati. Had she played those tournaments, winning one and at least reaching the semis in the others, she'd still have a comfortable lead.

Among the top three ranked women, Williams has the most points to defend at the U.S. Open. Last year, Kerber lost in the third round and Muguruza lost in the second.

Depending on where they finish at the U.S. Open, each has a chance to emerge from Flushing Meadows ranked No. 1.

But Kerber had her chance Sunday. She could have been the first German woman since Steffi Graf to reach No. 1. She would have also secured Graf's record of 186 consecutive weeks at No. 1. With Kerber's loss, Williams is guaranteed to tie Graf's consecutive weeks at No. 1. 

In anticipation of a change at the top, WTA officials had the No. 1-ranking trophy on hand in Cincinnati. Kerber would have been the first to win it.

The WTA came up with new No. 1-ranking trophies in October 2015, after Williams withdrew from the year-end event. One trophy goes to the player who finishes the year ranked No. 1. The other trophy will be given to any player ascending to the No. 1 ranking for the first time in her career. That's one trophy Williams is guaranteed to never win. 

With the trophy on standby and the No. 1 ranking within reach, Kerber turned in an underwhelming performance. 

It's as if the big moment is too much of a burden to bare. In assessing what happened to Kerber, Tennis.com's Ed McGrogan wrote: 

"

With the spotlight intensifying following her maiden major title, and after having dealt with illness during the clay-court season, Kerber has demonstrated what so many Top 10 players in the WTA have lacked: deep runs in big tournaments, week after week. And yet, can we consider her loss to Pliskova anything but a disappointment? 

"

If you include the Olympics, Williams has played in only eight tournaments in the last 12 months. During the same period, Kerber has played in 25 tournaments, including two Fed Cup ties and the Olympics. With such a chance to grab points, how is Kerber not No. 1 already? 

It's a testament to Williams' dominance from 2013 through 2015. It's been three years since Williams reclaimed the top spot. 

Williams has the most to gain at the U.S. Open. If she wins, she breaks the record for most Grand Slam titles in the Open era. She'll also break Graf's record for most consecutive weeks at No. 1.

With zero points to defend post-U.S. Open, Williams could play a couple of more tournaments, including the WTA championships, and then ride that No. 1 ranking into Melbourne with a shot at tying Margaret Court for most Grand Slam titles (24) of all time.

After defeating Williams at the French Open, Muguruza told Reuters (h/t Eurosport), "Everybody's dreaming about being number one. My focus is just on winning matches and tournaments. But of course I would be very happy to be number one."

In a column penned for Tennis.com, Steve Tignor wrote, "Kerber’s next opportunity to pass Serena and become No. 1 could come at the U.S. Open; if it does, we’ll find if she has learned anything about taking her chances when they come." 

So it's two women with a chance to make personal history versus an all-time great playing to be the greatest of all time. In this race for No. 1, the edge goes to Williams. She's captured it four times before and is one of the best at holding on to it.