Wales scrum-half Lloyd Williams faces a month on the sidelines after suffering a knee injury.
Williams, who provided bench cover for Mike Phillips during this season's successful RBS 6 Nations campaign, was hurt during Cardiff Blues' RaboDirect Pro12 defeat against the Ospreys at the Millennium Stadium last weekend.
"Cardiff Blues can confirm that scrum-half Lloyd Williams will be out of action for approximately four weeks following a knee injury suffered against the Ospreys over the weekend," the club announced on their official website.
The 23-year-old suffered grade two medial ligament damage, with a possibility that he could return to action against Ulster on May 3.
With Phillips set for a place in the British and Irish Lions squad to tour Australia this summer, Williams is favourite to wear Wales' number nine shirt against Japan in Osaka on June 8 and Tokyo seven days later.