Rosberg - winner in Spielberg for the last two seasons - crashed coming out of Turn 2 in the latter stages of Saturday morning’s session after what Mercedes confirmed to be a left-rear suspension failure.
As a result, the German's car will be fitted with a full new gearbox unit ahead of qualifying.
The Silver Arrows driver joins Sebastian Vettel in taking a five-place penalty into Sunday's race, after the Ferrari driver was also forced into an unscheduled gearbox change when metal filings were found in his unit following the last Grand Prix in Baku.
