US Open 2017: Angelique Kerber's fall shows weight of expectation at top of tennis

For the first time in over a decade, the US Open champion has failed to defend her title by being beaten in the first round.

Kerber has found it impossible to live up to the high standards she set herself in 2016, when she won Grand Slams in Melbourne and Flushing Meadows, and reached the Wimbledon final as well as picking up an Olympic silver medal for good measure. She finished the year as world number one even if she was unable to win the WTA year-end finals in Singapore, losing to Dominika Cibulkova in the final, and crowned the year by being named WTA Player of the Year.

Since then, Kerber has struggled hugely. She couldn’t claw her way past CoCo Vandeweghe in the fourth round of the Australian Open, and lost her world number one ranking immediately to Serena Williams. She was back on top of the rankings ladder by the end of May – and became the first world number one to get knocked out in the first round of the French Open, losing in straight sets to Ekaterina Makarova. Her fourth-round exit at Wimbledon – at the hands of eventual champion Garbine Muguruza – meant that Karolina Pliskova became the new world number one.

And now this first-round departure in New York - 6-3, 6-1 to Naomi Osaka - means that she will drop out of the Top 10 entirely.

The legendary Chris Evert – another former world number one – said earlier in the year that she thought the German needed to rid herself of nerves, rather than improve her game.

“For me it's nothing really to do with the physicality of her game," she said. "It's not that the game is not there, the same game that she won the Australian Open with and the US Open with.

It's no wonder that fear has crept into her game after such a plunge in form; it is a vicious circle. The weight of expectation for a world number one and Grand Slam champion is huge, and something to which Kerber was unused. She fought her way to the top of the mountain – but staying there is tough to do. Serena might make it look easy; Kerber has found that it is not.