Serena Williams was critical of herself after losing against opponent Bianca Andreescu in the U.S. Open Women's final Saturday.

Williams gave credit to Andreescu, but also added that she should have played better. 

"I think this is the worst match I’ve played all tournament. And it’s hard to know that you could do better,” Williams told reporters following the loss. “It’s inexcusable for me to play at that level.”

Williams fell behind quickly in the final and found it difficult to recover, losing 6-3, 7-5.

“She set the tone from the very beginning that she was not going to be pushed around,” Sylvain Bruneau, Andreescu’s coach, told USA TODAY Sports. “She’s not scared. She goes for it.”

Williams had 33 errors in the match, while Andreescu had 17, USA TODAY reported.

As she tried to get back in the game, Williams said she was telling herself, "this is terrible. You have to play better."  

“I could have just been more Serena today,” Williams said. “I honestly don’t think Serena showed up and I have to figure out how to get her to show up.”

Still, Williams said she will feel better about the match when she looks back in the future.

"In 20 years, I will look back and say 'wow, that wasn't so bad,'" Williams said. "It's very hard in the moment to say 'you did OK.' Because I don't believe I did. I believe I could have done more."

According to USA TODAY, this was Williams' fourth straight final loss since she gave birth to her daughter two years ago.

Williams said she has some similarities with Andreescu because both players are intense and passionate about the game.

"Bianca obviously played well. I think her returns make me play better and put pressure on my serve," Williams said. "At the same time it's inexcusable for me to play at that level."