The 7-times capped tight-head was stretchered off after just 35 minutes at Welford Road and X-rays have confirmed a fracture of the tibia.
The former Dragons star made the move down the M4 to rivals the Scarlets at the beginning of the 2009/10 season but missed a large chunk of that campaign with a toe injury.
The 28-year-old has been told he will be out until the New Year, ruling him at of possibly the next seven rounds of the Magners League and at least two Heineken Cup games.
The Scarlets travel to Cardiff this evening to face the Blues in a Welsh derby in round 6 of the Magners League.
