Sam Warburton, who led the British & Irish Lions to a drawn Test series with New Zealand in the summer, will undergo surgery following a recurrence of a long-standing neck injury.
The Cardiff Blues flanker exacerbated the injury in training this week and has undergone scans and has been reviewed by a consultant who confirmed the management plan.
It is likely that Sam will miss a period of up to four months. Warburton played 22 times in total last season but has been plagued by injury in recent times.
His absence is a huge blow for the Blues and Wales, with Warburton set to have been a key part of national head coach Warren Gatland's Test plans in November and December.
Wales launch their autumn series against the Wallabies in Cardiff on Nov. 11, before hosting Georgia, then the All Blacks and finally South Africa on Dec. 2.