Scotland and Glasgow Warriors prop Zander Fagerson will miss the bulk of the 2018 Six Nations after suffering a foot injury.
Glasgow revealed the prop, 21, 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 on March 10.
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.
There was better news for Glasgow and Scotland after Adam Ashe was included among the replacements for Warriors' PRO14 clash with Zebre in Italy after 10 weeks on the sidelines following ankle surgery.
Zebre have beaten Connacht and Ulster along with Southern Kings this season and head coach Dave Rennie had a warning for his players after they got back on track with a 17-0 win over Edinburgh following defeat at BT Murrayfield.
Rennie said: "Zebre have been impressive. In attack especially they lead the competition in a number of stats. They carry well, make a lot of line breaks and like to offload.
"They're a different team at home and have made it really tough for a lot of teams in Parma.
"We're going to have to defend really well and build on our ability to maintain pressure and go through the phases which was better last week."
There are new partnerships throughout Rennie's team with half-backs George Horne and Finn Russell plus centres Huw Jones and Nick Grigg starting together as pairs for the first time.
Alex Allan and Siua Halanukonuka start either side of Pat MacArthur in a new-look front row while Chris Fusaro and Greg Peterson also come into the pack.
Rennie said: "We've been a little bit thin in and around loose forwards so Matt Fagerson coming in last week and Adam coming back in this week is great."