Big names fell early and unexpected teams broke through to steal the spotlight on Day 1 of U.S. Open mixed doubles play, headlining an electric opener packed with upsets and standout performances.

The No. 1-ranked Sinner, the defending champion in singles at Flushing Meadows, was supposed to compete in mixed doubles with Katerina Siniakova.

The Spanish second seed snapped the world number one's 26-match winning streak on hardcourts when his ailing rival signalled he could no longer continue while trailing 5-0 in the first set.