At the age of 31, Serena Williams is as dominant now as she has been in the 13 years since she came on the scene.
To beat Victoria Azarenka as she did in the semis of the WTA Championships, and then to dismiss Maria Sharapova just as convincingly is quite something.
I don't think she's ever played as well in a tournament as she did in Istanbul. There was one sketchy performance against Li Na but apart from that it was a bulldozing affair.
When's she's like that there's no-one who can live with her. We saw a glimpse of that in Charletson, then she was frightening at the Olympics, and this was arguably even better.
She broke Azarenka's heart but we thought Sharapova could give her a game. And while she started well, Maria was blown away as soon as Serena stepped up a gear. The way she finished it off was so ruthless, so clinical, and it may well have affected Sharapova.
All they can hope for right now is that Serena has the occasional day like she did at Roland Garros with Virginie Razzano, Otherwise why can't she win all four next season? Right now she's the favourite for the lot of them — and the overwhelming favourite too.
Paris will be the toughest for Serena as it's her least favourite surface, but if she can maintain the kind of form we have seen in the latter half of 2012, you'd be mad to bet against her.
The problem for me is no-one can match her power and her serve, both first and second. Serena only has to break you once a set and she has the best serve and the most aggressive returns.
Petra Kvitova has that power but shows it nowhere near consistently enough. I think if she can get her head right, Kvitova and Angelique Kerber can join Azarenka and Sharapova in running Serena the closest. But no-one else has a prayer.
For me Serena is the best player of all time.
While I don't see anyone getting to Serena's level, I do think Kerber has the potential to beat the likes of Sharapova and Azarenka. She has significantly increased her mobility, and for her size has explosive power.
Losing five match points at Eastbourne was a worry but I haven't seen a sign of that since, and she is looking pretty solid when the chips are down. She seems to be improving month by month, but could she ever get to the level Serena is at right now? No.
One of the keys over the winter is how Li Na and Carlos Rodriguez work together. You could already see a lot of tweaks to her forehand and serve, but the important time is the next few weeks.
If the modifications settle well, Li could be a contender again. Agnieszka Radwanska has great hands and movement, but she lacks the size and power and needs the top girls to have an off-day.
It's been a fantastic year of sport and tennis for Britain, and the girls have more than played their part. I'm so surprised and so pleased with Laura Robson and Heather Watson.
Twelve months ago I could not have seen them progressing as they have this year.
I always thought Laura had the occasional big win within her grasp, but to do it as consistently as she has done was a big surprise.
She seems to be moving a lot better, she seems to have found some fight from somewhere, something I never thought she'd be capable of. She's a good match player now, not always going for ridiculous winners but able to build herself into points, and has the ability on that forehand to really be a thorn in top players' sides.
Heather's rise is quite astonishing really. Laura has the size, power and shots, but she needed to improve her movement and her head, and she has done that.
I thought Watson had reached a plateau, but every time she improves further, and with her maiden tournament win you have to marvel at her work ethic and guts. She's decided to take more risks with her shots and they're coming off, and she has a never-say-die attitude that is taking her beyond her ability.
I'd hate to put a limit on where they'll finish as both have proved me wrong already. Both are already qualifying for the Majors by right, and both are just a good run from being seeded. Get to the second week in Australia and have a solid start to the season and both girls will be top 30.
I saw Robson as top 50 at most but after what happened this year you have to change that. She could easily be a top 20 player. If the mental toughness cements itself, it could be top 10.
Watson is limited by her size but will find life a little easier now because of her ranking. I don't think she'll get vertigo as mentally she can cope. But it will be tougher for her to make that step into the top 20 — but she's proved me wrong before, so why not again.