Barty rises all the way to the top 

The biggest surprise of 2019 has to be that Ashleigh Barty finished the year as the WTA World No.1. That had not been part of the equation in anybody's mind and probably not even in hers. At the beginning of the year Barty said she was hoping to stay in the Top 20. Instead she won her first major this year at the French Open, reached the No.1 ranking and put an exclamation point on the year by winning the Shiseido WTA Finals Shenzhen and finishing with the coveted year-end No.1 ranking. Bravo! 

Osaka and Gauff's respect for each other 

There was a special, magical moment after Naomi Osaka beat Coco Gauff in the third round of the US Open. You'll remember how Osaka consoled Gauff, and then invited the American to be part of an on-court interview. I thought it was wonderful to see the new generation being so respectful of the game, and so respectful of each other. 

This new generation are fired up to win, and they are confident without being cocky, and they believe they belong, and they believe they can win. And they're combining that fire and competitive spirit with good sportsmanship. 

I hope the other players learn from them because I sometimes see players not doing proper handshakes and not looking their opponents in the eye after losing. I hope some players learn from the respect Osaka and Gauff showed each other. It does not cost you anything and it sends a good signal to the kids watching, and to the next generations, and quite simply it is the right way to be. So I am really encouraged by this new generation and how respectful they are, while competing so hard. I love that.

Andreescu holds her nerve

In my mind, the best match of the year was Bianca Andreescu beating Serena Williams in the US Open final, just because of the drama and because it was so unexpected. At the start of the season, I certainly had not picked Andreescu to win a Grand Slam in 2019, and I can not imagine anyone else did either - after all, she was outside the top 100 when the year began. The Canadian did not just win a major; she did it at the US Open and she did it against Williams in the final, and that's all the more impressive. 

When it looked as though Williams was coming back into the match, Andreescu held her nerve so well. She had gone into that match knowing that she could more than hold her own - perhaps encouraged by how Osaka had beaten Williams in the US Open final the year before. But to hold steady and then pull it out in the end, when playing in her first major final, that was truly impressive.

Halep's near-perfect tennis 

Simona Halep's performance in the Wimbledon final against Williams was close to perfect, and the performance of the year. That was the best I have ever seen her play from start to finish. She never wavered, she never had a bad game. She was a machine. Halep knew exactly what she had to do and then she executed it. It is one thing to make a plan against Serena Williams in a major final, and then another to do it. That was a great performance. 

Williams' disappointment 

In many ways, the year was pretty tough for Serena Williams, who did not win the 24th Grand Slam singles title she was so dearly seeking. While she reached two major finals, at Wimbledon and the US Open, she lost both matches. 

Great that she put herself in those positions, but Williams must be disappointed that she came so close and then did not play her best tennis when it mattered most. It is tough when you get so close but can not punch it through. And it gets harder as you get older. So now when Williams reaches her next major final, it is going to be a question of whether she can play her best tennis when it matters most. More than anything else, it is mental more than physical. But as we know, Williams can come back with a vengeance so I expect her to be strong in 2020.