It means the All Whites, confidence severely undermined by two successive Heineken League defeats, will be without their master tactician against the cup kings.
Jones's absence through a nagging shoulder injury sees David Weatherley, the Wales Under-21 cap, promoted to a duel with Rupert Moon, the current Welsh scrum-half, in a key area. If Moon is allowed to break close to the fringes and link with his back row, the Scarlets will be on their way to a fifth appearance in the final in six years.
'That's a nice surprise,' was the reaction from Moon, Llanelli's captain, to the news that the man he ousted from the Welsh No 9 jersey in France would not be risking his shoulder.
'It is unfortuante that he's going to miss the cup tie, but I know that if I was in his shoes and there was a doubt over my shoulder I wouldn't risk missing a Lions tour.'
Not that Moon expects the loss of Jones to change Swansea's commitment to the Arms Park semi-final. He merely expects it to add to their 'wounded animal' philosophy.
'After those league defeats at Pontypridd and Aberavon they are like a wounded animal. We were in a similar position to them in January when we played at St Helen's with a number of injury problems,' Moon said. 'They showed no sympathy for us then and I don't expect my side to offer them any now. Swansea have got nothing to lose while we are chasing a cup and league double.'
Victory in Cardiff would set up Llanelli for Wednesday's home match with Pontypridd, from which one point would give them the First Division title. Defeat could undermine confidence and even allow Swansea or Cardiff to steal the prize today week.
While a repeat of last season's final has dominated headlines, Neath and Bridgend have been preparing quietly for their tie at Stradey Park. Neither will look out of place in the final on 8 May, although predicting a winner is a precarious business. Neath have been shocking away from The Gnoll this season, but they did manage the double over Bridgend in the league.
Bridgend, meanwhile, have staged a miraculous recovery this season under the guidance of Clive Norling and are already in line to take the award for the most improved team.Reuse content