Venus Williams may have lost in straight sets to little sister Serena in the third round of the US Open - but she's not too disappointed as she says there's nothing she could have done better.

"I think it’s the best match she’s ever played against me," she told reporters afterwards as she reflected on the 30th meeting of their careers.

LOOK: Story of the match - Serena vs Venus, Part 30

"I don’t think I did a lot wrong. But she just did everything right. Obviously that level is definitely where she’s going to want to stay during this whole tournament.

"I mean, she played so well, I never got to really even touch any balls. When your opponent plays like that, it’s not really anything to be upset about.

"The only thing I maybe could have done was put more first serves in. Even then she returned the first serve really well. Any shot that I hit great, she hit a greater shot. Not a lot I can do."

For her part, Serena praised her 38-year-old sister as the best opponent she has ever played - and says each win means more now as they come towards the latter stages of their on-court careers.

"I feel like we want it so bad now.  I mean, we wanted it really bad when you were younger but we had a lot more years in our future," the 36-year-old said.

"Now, I mean, we definitely want to continue to play, but it’s not like we’re 18 and 19 any more. So it’s a little bit different."

Serena also felt it was her strongest performance since returning to the sport in March after the birth of her daughter.

"I played much better tonight than I have since I started this journey on my way back," said Williams, who reached this year's Wimbledon final.