On September 12 of this year, German Angelique Kerber ended the 186-week reign of Serena Williams at the top of women's tennis.

Despite Williams reaching and holding the world #1 mantle on three separate occasions, each five plus years apart (2002, 2008 and 2015), it still felt like a significant shifting of the balance of power in the WTA, in a landmark year for the tour.

This year, Kerber was by far the pre-eminent player on tour, and was rewarded with the #1 year-end ranking.

However, even she was defeated in three of the major tournaments up for grabs this year – The Championships, where she was defeated by Serena, the Olympics, defeated by Monica Puig, and the WTA Finals, defeated by Dominika Cibulkova.

The other major title of the year, Roland Garros, was won by a 23 year old Spaniard by the name of Garbine Muguruza.

Competitiveness is back at the top of the women's tour, and it is long, long overdue.

We have finally made it back to a state of play where any of the top 10 players in the world can legitimately win any of the four Grand Slams contested.

Each one of the top seven players on tour has been to at least one Slam Final before, with world #9 Svetlana Kuznetsova having also won 2 Grand Slams previously, and Madison Keys and Johanna Konta both having made the semi-finals.

By the way, Konta and Keys are 25 and 21 respectively. To say they have big futures ahead of them is an understatement.

Of the players ranked 11 to 20, there are 11 Slams shared between them. That's without counting Caroline Wozniacki, former world #1 who has failed to win a major but is steamrolling back to her 2010 self.

Perhaps what separates the women's tour from the men's the most is the distinct style of play represented within the top 10.

Whilst serving and defence dominate the men's game, the women's game represents many different takes on a successful game plan, all of which are proven to prosper against the others at the top of the tour.

Angie's defensive counter punching game has no doubt ruled the roost this year, but at different times so has Williams' overwhelming power, Agnieszka Radwanka's brilliant point construction and Simona Halep's aggressive baselining.

Despite all this, what is perhaps most encouraging for the tour is the answer to a perplexingly shortsighted question asked by many casual fans each year – what is to become of the WTA once Serena retires?

Without diminishing what one of the greatest of all time has done for women's tennis, we now have an answer – it will be as healthy as anyone ever believed it could be.

So, off the back of a mightily and pleasantly surprising and successful year for the women's tour, all of us will now be wondering what the WTA may serve up next year.

The truth is, for the first time in perhaps a decade or longer, we can finally say, “we don't know”.

Will Kerber be #1 this time next year? Will 27-year-old Radwanska finally break through for her so deserved maiden Grand Slam title? Will Muguruza fulfill her all court promise and win a hard court Grand Slam?

Who knows; anything could happen.