When 2025's mixed doubles event at the US Open starts on Tuesday, one name will be surprisingly absent from the list -- ATP World No. 1 Jannik Sinner.

Grand Slam singles champions such as Jannik Sinner, Carlos Alcaraz, Iga Swiatek and Madison Keys will be playing for a little extra money — OK, a lot of extra money, by any standard: $1 million to the winning duo — and trying to get their hands on a trophy in the U.S. Open’s overhauled mixed doubles tournament.

When it came to finding a partner for the newly formatted mixed doubles event at this year’s U.S. Open, it seemed like a no-brainer for Madison Keys.

Emma Navarro withdrew from the mixed doubles championship at the U.S. Open, but Katerina Siniakova will replace her and partner with Jannik Sinner.