Neath switch Gareth Llewellyn, their captain, from the second row to No 8, while the cup holders, Llanelli, have opted for the 6ft 8in Paul Jones at blindside flanker.
It means both will have stacked line-outs and larger than usual back rows. Llewellyn's move means that Steve Williams, the Wales A No 8, moves to the blindside and Mike Whitson comes into the second row, while Jones packs down alongside Scott Quinnell, the Wales No 8, ahead of Lyn Jones, the former international breakaway.
Having conceded defeat in the race to retain their Heineken League title, Llanelli know their season will effectively be over if they fail to repeat their cup final success of last May against Neath.
For once they go into a cup tie as firm underdogs, but in this competition nobody performs better than the Scarlets. Winners the last three seasons, they will be looking for their 20th successive victory in a sequence of triumphs stretching back to 1990.
But Neath, who pushed Llanelli close in last season's final, have
already beaten them at The Gnoll in the league this season and, even without Brian Williams, their inspirational prop, they look to have too much power up front for their visitors to contain.
'Neath love to play the game at 100mph and to overwhelm their
opponents. What we must do is slow them down, tie them in and move the ball wide,' Ieuan Evans, the Llanelli and Wales wing, said.
'It will be unusual for us to go into a cup tie as the underdogs, but Neath deserve to be the favourites because of the way they have been playing this season. Our form has been very patchy.
'But the cup tends to bring out the best in Llanelli teams and we also perform to our best when we are up against it. That is the sign of a good team and good players.'
Having slipped up in their
attempt to take the league title by losing away to Swansea, Neath are bound to be fired up for the cup and keen to repeat their 27-5 victory of 20 November.
Whoever wins at The Gnoll will be favourites to win the cup, although everyone will want to avoid Pontypridd in Tuesday's semi-final draw should they beat Newbridge at home. With 13 straight league and cup wins, they are the form team and, in Neil Jenkins, have the country's leading scorer.
At least one Second Division team will reach the semi-finals for the first time thanks to the pairing of Maesteg and Tenby United. Another, South Wales Police, get their chance against Cardiff on Tuesday.Reuse content