Scotland prop Zander Fagerson will miss the bulk of the NatWest 6 Nations after suffering a foot injury.
Glasgow, who will play Leinster in the Champions Cup on 14 January, revealed the 21-year-old would be out for up to eight weeks after an accident in training.
Scotland face Wales, France and England in February and Fagerson could also struggle to be fully fit in time to face Ireland at the Aviva Stadium on 10 March.
Fagerson already has 15 caps and was an ever-present for his country throughout 2017.
Warriors suffered a triple blow with Callum Gibbins and Scott Cummings also facing lengthy spells on the sidelines.
Gibbins has undergone surgery after an Achilles problem halted the flanker's impressive start to his Scotstoun career. Warriors say the New Zealander faces up to 12 weeks out.
Second-row forward Cummings will be out for about eight weeks after suffering a hand injury in training this week.
Meanwhile, Saracens and England have received a major double boost with Billy Vunipola and Maro Itoje returning from injury on Sunday.
Powerful number eight Vunipola has been sidelined since September because of a knee injury, raising concerns that he might not be fit for the start of this season's Six Nations.
Lock Itoje, meanwhile, broke his jaw a month ago, but Saracens have announced both players in their starting line-up for the Ricoh Arena appointment with Wasps.
It also means they are available for Saracens' final two European Champions Cup pool fixtures against Ospreys and Northampton, with the holders realistically needing victory in both matches to keep alive quarter-final ambitions.
Vunipola missed the Lions' New Zealand tour last summer because of a shoulder problem, but his latest comeback begins a month before England's opener against Italy in Rome.
