Rees was capped on Wales' summer tour to North America

The injury adds to concern over the number two jersey at Stradey Park, with Robin McBryde waiting to hear if his career is over following back surgery.

Promising youngster Aled Gravelle is available on the Scarlets' books.

Meanwhile Scarlets coach Gareth Jenkins said there were "many positives" from the 20-24 friendly loss to Worcester.

"It obviously nice to win these games, but it is more important to find out where you are or where you aren't with a couple of weeks to go before the start of the season," said Jenkins after Saturday's defeat at Stradey.

"We were desperate for this game and what we have found out is that our line-out is not what it needs to be.

"It is an area that needs to be addressed over the next week or so.

"There were a lot of pluses. Regan King was a major plus, and it was nice to see Dafydd James back.

"I was able to see Hottie Louw and Inoke Afeaki play for the first time and also a number of our younger players."