Hughes,, batting for South Australia, collapsed face first on the ground after being hit by the bouncer from Sean Abbott during a Sheffield Shield game against New South Wales.
He was treated on the pitch before being rushed to St Vincent's Hospital in Sydney where he underwent a 90-minute operation to relieve pressure on his brain.
Doctors did not give details on the extent of Hughes's injuries but the Australian Broadcasting Corporation said his skull was fractured and the Sydney Morning Herald reported that he had suffered catastrophic bleeding in his brain.