Scarlets prop Deacon Manu has been sidelined for at least three months after learning he needs surgery on his broken arm.
The Fiji international left the field late on in last weekend's 26-10 victory over Treviso with a recurrence of the injury he suffered more than two years ago.
X-rays at the time revealed a fracture, and further tests have determined the full extent of the problem.
"It's a pretty clean break, but it's broken where one of the screws goes in, so there are a couple of different options," Scarlets coach Simon Easterby told the South Wales Evening Post.
"It looks like he'll have an operation on Friday, but he's looking at anywhere between 12 and 16 weeks out.
"Cover is something that we will have to look at. The Heineken squad went in on Wednesday so it's disappointing to lose someone of Deacon's experience. We'll have to look at how we manage that situation.
"Rhodri Jones is going really well at tight-head for Llanelli at the moment, he's getting plenty of game-time.
"We probably will also look at bringing someone in."
Aside from Jones, Samson Lee and South African Jacobie Adriaanse is another option at tighthead.
20-year-old Lee started in the number three jersey against Treviso but went off with breathing issues at half-time.
The problem is not serious, however, and he is back in contention for this weekend's clash with the Dragons at Rodney Parade.
"Samson's good," added Easterby.
"He had something caught in his throat and he was struggling to catch his breath.
"There was a bit of panic because he went down straightaway, but it was simple enough and easily rectified once we got him off the pitch and realised what it was."
Apart from Manu, centre Gareth Maule (knee) and wing Kristian Phillips (hand) are also on the injury list.
But scrum-half Rhodri Williams is back in contention after missing the Treviso game with a shoulder complaint.
Back-rower John Barclay could also play his first game this season, after recovering from surgery on a similar problem.
"He's in full training and it'll be good to have him involved," said Easterby.
"He's desperate to get out there and put a marker down. He's been doing quite a bit lately, but to get that all clear from the surgeon was the important next step.
"He's had that, so there'll be a decision now about whether we start him or pick him on the bench."