However, referee Thomas Kirk will continue to monitor conditions ahead of kick-off, with heavy rain currently continuing to fall in Oxford.
There are wet patches along the touchline of the pitch at the Kassam, as well as in one of the goalmouths.
Kirk is happy with conditions as they stand, but the forecast is for more rain ahead of kick-off, which should ease as the afternoon continues.
Sunderland are taking on Championship Oxford for a place in tomorrow's fifth-round draw, having beaten Everton on penalties in round three.