It will be the third quarter-final they have played with honours even so far, though and have met four times in the final round with two victories each - Neath in 1972 and 1989 and Llanelli winning in 1988 and 1993.
Llanelli's amazing record has seen them win the cup on eleven occasions and win 133 of their 153 ties, including both meetings with Neath at Stradey - the last by 40-17 in a 1998 quarter-final.
Neath have won 93 and lost 28 and taken the cup on three occasions. They could have Hywel Jenkins back from injury at No 8 and will be skippered by lock Gareth Llewellyn, while Llanelli have former flanker Aled Gravell pressed into service as hooker with both Robin McBryde and Marcus Thomas injured. Forwards David Hodges and Luke Gross are involved in World Cup play-off matches for the USA against Spain with Wales prop Iestyn Thomas has suffered a neck niggle and is named on the replacements bench.
Llanelli: B Davies; G Evans, M Watkins, L Davies (capt), S Finau; S Jones, D Peel; P John, A Gravell, M Madden, V Cooper, C Wyatt, D Jones, S Easterby, S Quinnell. Replacements: I Thomas, J Davies, J Cudmore, I Boobyer, G Easterby, G Bowen, T Selley.
Neath: (from) Backs - G Morris, K James, J Storey, A Durston, D Tiueti, S Williams, S Connor, P Horgan, A Moore. Forwards - A Millward, A Matthews, P James, S Jones, A Jones, A Newman, L Bateman, G Llewellyn (capt), A Mocelutu, J Ringer, S Tandy, R Phillips, H Jenkins.
LLANELLI v NEATH (at Stradey Park, 5.30pm).
Previous cup meetings: Llanelli lead 7-3.
1971/72 Neath 15 Llanelli 9 (final); 1972/73 Llanelli 6 Neath 3(semi);
1986/87 Neath 15 Llanelli 3; 1987/88 Llanelli 28 Neath 13 (final);
1988/89 Neath 14 Llanelli 13 (final); 1990/91 Llanelli 22 Neath 10 (semi);
1991/92 Llanelli 28 Neath 9; 1992/93 Llanelli 21 Neath 18 (final);
1993/94 Neath 3 Llanelli 7 (quarter); 1997/98 Llanelli 40 Neath 17 (quarter).
Llanelli have won 133, lost 20. Cup winners 11 times, runners-up four times.
Neath have won 93, lost 28. Cup winners three times, runners-up five times.
Llanelli beat Pontypool 30-22(a). Neath beat Glamorgan Wanderers 76-12(a).