"Three of our first string tight heads are now not available to us. We are going to have to re-group and see what options we have to move forward," said Scarlets coach Nigel Davies.
"Over the course of the season we are going to have ups and downs with results, and we weren't happy with the result against Leinster because it was a game we should have won. But our biggest concern at the moment for us are the injuries."
Edwards suffered a suspected broken fore-arm in the first half and then his replacement, Manu, was carried off in the second half after his right arm collided with the head of a Leinster player.
With Thomas two weeks away from any potential return to action it looks as though the Scarlets could have to mix and match their remaining front row forwards - Iestyn Thomas, Phil John, Richard Jones and Simon Gardiner. Of that quartet, only Wales Under 20 cap Gardiner is a recognised tight head.
A win on Friday evening would have sent the Scarlets to the top of the Magners League but they must now turn their attention to European action and back-to-back games against Benetton Treviso over the next two weeks.
The Scarlets travel to northern Italy this weekend, to a ground they have already lost in this season, before welcoming Treviso to South Wales the following week.