NEW YORK -- With a US Open title, Barbora Krejcikova and Katerina Siniakova have won every big title in the sport. 

Krejcikova, Siniakova rally to beat McNally, Townsend to win US Open

The Czech duo completed their career Golden Slam, with wins at each of the four Slams and an Olympic gold in Tokyo last year. They also won the doubles title at the WTA Finals last year in Guadalajara, Mexico, and have been integral parts of the Czech Republic's Billie Jean King Cup dynasty. 

Seeded No.4 at the US Open, Krejcikova and Siniakova reunited to close out an undefeated season at the Slams. The team went 18-0 to win the Australian Open, Wimbledon and US Open. Their season could have been one for the record books if not for Krejcikova testing positive for Covid at Roland Garros, where they were the defending champions.

Here's what Krejcikova and Siniakova had to say after their latest win:

WTA Insider: Why do you think the US Open was the toughest Slam for you to win?

Krejcikova: I don't think it actually was the toughest one. I think we just went step by step. I will say the Aussie Open was really tough for us as well. All the other Slams were tough, too. We just needed the right time to achieve all of that.

WTA Insider: Why was this the "right time"? 

Siniakova: There is no right time. We were just working and practicing and trying every time to show our best on court. This time we played great. We kept working and even if it wasn't going our way, we kept fighting. I'm just so happy we have the title. I think "keep fighting" is the key. I don't think there is a right time; it's just sometimes it clicks together. 

WTA Insider: You've won every significant title in the sport. What's your next goal?

Krejcikova: I think the goal is mainly to improve every single time we step on the court. When we are playing and we win titles it's amazing satisfaction for that feeling that you are working and improving. I think there's a lot of motivation for us to step on the court and try and get better again and improve in doubles together. I believe that next time we are going to go to another big tournament we'll just have the motivation to fight again. It will be a new result. Just try to win more Slams and do well. 

WTA Insider: Of all your titles, which one means the most to you?

Siniakova: It's so tough to compare them because every one has memories and journeys that are different. I don't know if I can choose one. I appreciate all the titles we won and the incredible journey and memories. I'm just enjoying that we're doing so great. 

Krejcikova: It's tough to say. All of them mean a lot because they're really hard and you have to be really consistent for two weeks. It's super difficult to be difficult for two weeks. 

But if I had to choose I would say the Olympics because it's once in four years and it's really difficult to prepare the form and do the best out there once every four years.