The former Reading man sustained the injury in the first half of Saturday's 3-1 win over the Saints, leaving the field on a stretcher to be replaced by Dickson Etuhu.
It was the second time Hughes has been injured in matches against the Hampshire side, the clash at St Mary's having put him out for three weeks earlier in the campaign.
The injury will stretch the midfield resources at Carrow Road as Youssef Safri will depart in January for the African Nations' Cup, although Nigel Worthington is sure to look at options to bolster his squad for the rest of the season once the transfer window opens in the new year.