NEW YORK, NY, USA - Bianca Andreescu showed great poise to win her first Grand Slam title. When Serena Williams was coming back at her, and when 23,000 New Yorkers were going crazy inside the US Open's Arthur Ashe Stadium, the teenager kept her head together. That was the mark of a champion.

I think Serena was a little surprised by how well Andreescu, playing in her first major final, handled everything. Having had a match point at 5-1, Andreescu lost four games in a row, taking the score to 5-5, and if the Canadian had lost her serve again, Serena would probably have gone on to take the match. But, even in that atmosphere, and under such enormous pressure, Andreescu was able to shut everything out and concentrate on what she needed to do. Andreescu just stayed on her own side of the net, only focused on playing ball. Everything else didn't matter.

It was as if Andreescu knew that there was nothing she could do about the crowd being so vocal in their support for Serena, and she didn’t take it personally though it must have been hard, really hard. That was impressive. Andreescu, even though she had never been in that situation before, whether playing in a major final or the crowd being that one-sided, just got on with it.

If Andreescu had taken her first match point, she would have won 6-3, 6-1, and it would have been a straightforward final. Serena hadn't really shown up until that point. Then, suddenly, Serena did show up. In the end, maybe it was more satisfying for Andreescu to take that second set 7-5 because she had to fight for it. You take a win any which way you can, especially in a major, but maybe it was more of a learning moment for her because she had to hold off Serena. Whenever there was a big point, Andreescu played it really well. She went for her serve; she went for her return. Other than backing off ever so slightly for those four games from 5-1 to 5-5, Andreescu didn't flinch.

While Andreescu has great variety in her game, she didn't use it all that much in the final. I think she only hit one dropshot all match. She didn't use that variety because she didn't need to. She didn't need to disrupt Serena's rhythm; Serena didn't have that rhythm in the first place.

If Serena plays her best tennis, she's still better than everybody else out there. Unfortunately for Serena, she didn't do that in New York. The biggest problem for Serena was that her serve - which is almost always her biggest weapon and her go-to shot - failed her. When Serena faces break points, she is used to her serve helping her out - an ace or an unreturnable serve is the norm. On this occasion, Serena double faulted instead. The first three times she lost her serve it was on a double fault - never have I seen her do that before.

If you have a weakness in your game, and it's off, you kind of accept it and deal with it. But when your best shot breaks down, you're left thinking: 'What do I do now?' That makes it difficult to find your rhythm. Also, when your serve goes south, it can be distressing emotionally, and it can be embarrassing. You're the one in control with your serve; no one is making you miss. It's all on you. The serve has been such a big weapon for Serena so the fact it broke down was really significant for her, and she didn't quite recover from that.

Naturally, Serena was nervous, on her fourth attempt in a final to equal Margaret Court's all-time record of 24 Grand Slam singles titles. That kind of pressure only happens to legends and is impossible to quantify. It’s a very lonely feeling. But, after saving that match point at 5-1 down, she almost overcame it and nearly went on to pull a rabbit out of the hat. But it was, as they say, too little too late.

I still think Serena can get to 24 majors, especially as the court surface at the Australian Open suits her better as it's faster than the US Open. But, after losing four in a row, every major final is now going to be harder for Serena. For one thing, there are going to be more players who think they can beat her. And also the scar tissue and the pressure will only grow. Just 'Average Serena' is not going to cut it in Melbourne in January; she will have to bring her best.