Serena Williams has shown everyone that she lacks no desire or character in playing through immense humidity and pain to win the WTA Championships in Doha.
I think Serena has always tried her best, but sometimes in tournaments outside the Grand Slams she cannot find the adrenaline she needs. This can lead to some people harshly questioning her temperament or hunger, which is utterly ridiculous.
In many ways this was her most commendable performance of the year because she played through a lot of pain and showed tremendous desire to win.
It was a super display from Serena to beat her sister Venus in the final and round off a very challenging and gruelling tournament.
The Williams sisters' match on Wednesday was extremely poor, and sometimes they simply have too much respect for each other. There is occasionally a macho element between the pair and their games suffer.
But in Doha, it was a splendid final and not like the shoot-outs their encounters can often be: both played sensibly and provided a fine spectacle.
I think it is of huge significance for the players who ends the year as world number one, and Serena is no different.
Being on top of the world at the end of the year is something which goes down in history and Serena has, quite astonishingly, only achieved that once before.
Clearly the American was utterly determined to secure the number one spot and, even after she had achieved it midway through the tournament, she kept the fire burning within her.
Serena was clearly in a great deal of pain with her leg very heavily strapped, but her focus and resilience - in spite of the injury - made her victory all the more impressive.
She was wincing at her sister Venus on many occasions and Doha looked like a casualty ward by the end of the tournament: everyone will be relieved to end the year now.
It is good for the game to have both Williams sisters busting a gut out there and, although sometimes they cannot give of their best, they found the motivation required to keep a high intensity.
In the context of Serena's career as a whole, 2002-03 has to be seen as her golden period when she won four consecutive Grand Slams.
Back then she was the best player in the world by a country mile and if she had kept that focus she could have utterly dominated women's tennis for a good three or four years.
I do not think Serena is capable of finding that level again because with Kim Clijsters and Justin Henin returning, and Maria Sharapova finding a resurgence, she has some stiff opposition.
We are not embarking on a period of dominance which we saw in 2002 from Serena, and there is no way that she will be able to sustain such a high level and stay injury free all the time.
That said, she has impressed everyone with her grit and determination in Doha and women's tennis is lucky to have her showing such commitment and desire.
The American thoroughly deserves to end the year as the world number one and her effort or dedication should never be brought into question again.