Scarlets wing Harry Robinson will undergo surgery after sustaining a "significant neck injury".
Robinson, the region's top try scorer this season with 13 tries, is expected to be out of action for up to four months.
The 22-year-old, who has won three caps for Wales, joined Scarlets from Cardiff Blues at the start of the season.
Fly-half Steven Shingler and prop Peter Edwards will both undergo shoulder surgery.
They are expected to return to action in August, as are wing Jordan Williams and hooker Emyr Phillips, who have also had shoulder surgery.
Scarlets have also reported prop Samson Lee's Achilles injury is progressing well and the 22-year-old will continue his rehabilitation with the Welsh Rugby Union's medical team.
Lee suffered the injury in Wales' 23-16 Six Nations win over Ireland in March.