His club Rapid Vienna said Austrian striker Guido Burgstaller suffered a fractured skull when he was attacked in the center of the country’s capital.
Rapid said the 35-year-old is expected to be out of action for several months after suffering a “serious head injury” at the weekend.
They say the former Cardiff City striker was attacked by an “unknown man” and suffered a fractured skull when he fell after a “brutal blow”.
The 35-year-old, who played for Austria 26 times, was examined at the scene before being taken to hospital, where he will stay for the next few days.
In a statement, Rapid said it was “confident in the responsible authorities that the still unknown perpetrator will be quickly brought to justice”.
Burgstaller joined Cardiff from Rapid in 2014, becoming Ole Gunnar Solskjaer’s second signing for the Welsh club.
He only appeared three times for the Bluebirds before joining German club Nurnberg.
Bugstaller also played in Germany for Schalke and St Pauli before returning to Rapid in 2022.
He was one of three Austrian players dropped by coach Ralf Rangnick in 2023 after they were filmed singing homophobic slogans following a 3-0 win over cross-town rivals Austria Vienna.
