Rain forced postponement of 22 US Open second-round singles matches Wednesday, delaying court action for such stars as Russian fifth seed Daniil Medvedev and three-time Grand Slam winner Stan Wawrinka.

Matches were conducted under the roof at Arthur Ashe Stadium and beneath the roof at Louis Armstrong Stadium. Roger Federer, Novak Djokovic, Kei Nishikori, Ashleigh Barty, Karolina Pliskova, Elina Svitolina and Madison Keys advanced to the third round on Wednesday. Serena Williams’ match was still going on.

But only 10 matches will be staged, pushing 22 more to Thursday’s already planned 32 singles matches.

Three matches began on outer courts before showers struck the decisive blow. They will be completed Thursday.

Medvedev will meet Bolivia’s Hugo Dellien while Wawrinka will play France’s Jeremy Chardy.

The scheduled start of US Open doubles matches was washed out completely.