Scarlets back row Rob McCusker faces a race against time to fit for his region's next two Heineken Cup matches in December.
The 24-year-old had been named in Warren Gatland's Wales squad for the autumn international series but will undergo a hernia operation next week, ruling him out for six weeks.
"The decision has been taken for Rob (McCusker) to have surgery sooner rather than later to give him a chance of returning to the international scene in time for the Six Nations Championship and therefore bid to make the 20100 Rugby World Cup squad," said Wales physio Mark Davies.
The Scarlets face back-to-back fixtures against Italian side Benetton Treviso in December when European's premier rugby competition returns for Rounds 3 and 4.
The Welsh side will be looking for revenge in Northern Italy after suffering defeat at the Stadio Monigo in the opening fixture of the celtic league competition.
The Pool 5 side started this year's Heineken Cup in dramatic fashion, beating French side Perpignan in a nine-try thriller at Parc Y Scarlets, but went down to a clinical display by double European Champions Leicester in Round 2.