SERENA WILLIAMS has broken so many records that it’s hard to keep track of them all. She is on the verge of breaking one of the most significant, though. Currently, Steffi Graf holds the record for most consecutive weeks at world No.1 in women’s tennis – 186 – which she set between August 1987 and March 1991. Williams has been world No.1 for 184 weeks and, with the US Open beginning on Monday, she is guaranteed to reach 186 to tie with Graf.

It is hard to over-state just how impressive a run this has been for Williams, particularly when you consider that her tournament schedule is significantly lighter than the majority of her rivals. The American is considered to have had a somewhat fallow time of it this year; she has won only one grand slam and been beaten in the two other major finals – that this is still considered sub-par says much about the lofty standards that she has set for herself.

There are a number of players who profess to care little about the No.1 ranking, stating that major titles are their only motivator. Williams is not one of those players; breaking Graf’s record for most consecutive weeks at the top is, she admits, a target. However, she is in severe danger of losing the No.1 ranking over the next two weeks with her main challenger the world No.2, Angelique Kerber. The German has had the best year of her career; she began 2016 by winning her maiden grand slam title at the Australian Open and then reached her second grand slam final at Wimbledon. The German won Olympic silver a few weeks ago and when she reached the final of Cincinnati last weekend, the No.1 ranking was within the 28 year-old’s grasp. A surprising loss to Karolina Pliskova meant that Williams hung on to the top spot but it may only be a stay of execution for the American.

Williams currently holds a 190 point advantage over Kerber in the world rankings but she has significant points to defend at the US Open; the American reached the semi-finals last year while Kerber reached only the third round. There are a number of permutations for the No.1 ranking but the most significant are that if Williams wins the title, she remains No.1. If Kerber reaches the quarter-finals, Williams must reach at least the final to retain the No.1 spot. And if the final ends up being a battle between the world’s top two, whoever claims the title will also take the No.1 spot.

While Williams’ run in the top spot has been remarkable, Kerber displacing her may be a godsend for women’s tennis. Williams has suffered from a real lack of rivalry in recent years and women’s tennis has been all the poorer as a result. Kerber looks to have both the game and the mentality to give Williams a sustained challenge; the German has risen from 15th spot at the end of 2015 by consistently making runs deep into the big tournaments. She also has the mentality to challenge Williams on the biggest stage in the game; grand slam finals, something that cannot be said of all the WTA players.

Women’s tennis, and Williams in particular, needs a rivalry. In recent years, despite being well into her thirties, the American has accumulated grand slam titles at quite a rate, often with little resistance. Many agree that Williams is the greatest woman ever to play tennis but the latter part of her career has suffered with the absence of a primary challenger. Garbine Muguruza has shown signs that she has the potential to be world No.1 but she remains inconsistent. Agnieska Radwanska and Simone Halep can barely lay a glove on Williams. And almost all the rest of the American’s losses are as a result of her playing well below her best. It is not a great advert for women’s tennis.

But Kerber is different. In recent months, the German has managed to harness her obvious talents and her results have improved significantly. With impressive speed, spin, power and stamina, Kerber has the beating of anyone. This is something that few others can claim. Her profile remains low outwith tennis but Germany is desperate for someone to recapture the glory days of Graf and Boris Becker and while Kerber will not equal them, further grand slam titles are likely. The women’s game has suffered in the past decade because it has been constantly compared to the men’s, which has enjoyed a golden spell with the ‘big four’ that may not be seen again for a generation. However, the era of the big four is coming to an end and so there is an opening for the women’s game to grab some of that attention. Williams is likely to not be around for much longer. If her last few years on tour were marked with an intense rivalry with Kerber, both women’s tennis and the American herself would be all the better for it.