Under-19 World Cup: High stakes for the Paul Ryan captained Irish team. Defeat here could see Ireland sink into the ninth to 12th play-off category for what would be a depressing last week of competition. That's the worst case scenario, however.
Victory with a bonus point and the host nation could qualify for a crowd pulling semi-final against New Zealand side or Australia next Tuesday at Ravenhill.
A win without four tries could still deliver a top-four finish providing France and England lose without gaining any bonus points against the Wallaby's and Baby Blacks respectively this evening.
Otherwise it's a repeat of last year in Dubai where Ireland won the fifth-place play-off.
Ahead of what promises to be a monumental battle - South Africa are in an equally precarious position - Ireland coach Charlie McAleese has made four changes for their third game in eight days. Two of which are injury enforced.
St Michael's College captain Conor Cleary is ruled out with an ankle strain so Murray Kinsella starts at inside centre.
Trinity prop Patrick McCabe replaces Paul Nelson, who lasted just 19 minutes in Monday's 13-12 victory over Scotland after sustaining ligament damage to his neck.
"We've had a few injuries but we always were going to have some when bringing boys out of schools to play against young men," said McAleese.
Other switches see UL Bohs lock David Foley replace Brian Cawley, while Ballymena fullback Jamie Smith is preferred to Adam Craig.
In terms of physicality and tempo, the Australian defeat would have been a rude awakening for the Irish teenagers, who showed well in defeat, before dropping their performance levels considerably against Scotland.
Former Belvedere schoolboy Eoin O'Malley, now UCD, has been the stand-out performer thus far but, along with outhalf Scott Deasy, he must impose a territorial game on South Africa.
Failure to produce penetrative kicking tactics and Ireland's embattled forwards will be drawn into repetitive confrontation where the larger opponents should eventually prevail.
McAleese added: "We don't overplay the physical disadvantage beforehand just in case the psychology works against us but we do make demands of them. We ask them to put their bodies on the line. They have responded well to the physicality. Certainly, the Australia game proved we are well able to match it if we are organised and get our intensity levels up."
This group showed spirit against Australia but the intensity levels eventually took their toll. Enthusiasm alone will not suffice tonight. To overcome a far from vintage South Africa - who dealt with Fiji, 36-5, before losing to France, 17-8 - Ireland must combine their glimpses of quality with consistent control of territory. Anything short of victory will ultimately class this tournament as a failure.
IRELAND: J Smith (Ballymena); N Morris (Blackrock College RFC), E O'Malley (UCD), M Kinsella (Newtown School, Waterford), P Brophy (St Michael's College); S Deasy (PBC Cork), H McAleese (Ballynahinch); P Karayiannis (RBAI/QUB), S Douglas (Ballymena), P McCabe (Dublin University); D Foley (UL Bohemians), I Nagle (Glenstal Abbey); K Essex (CBC, Cork/UCC), R Reilly (St Michael's College), P Ryan (Blackrock College RFC, capt). Replacements: M Sherry (Ard Scoil Rís/Garryowen), I Leonard (St Michael's College), M Nelson (Ballynahinch), B Cawley (UCD), J Harris-Wright (Blackrock College), P Mallon (St Michael's College), A Gaughan (Buccaneers), T Seymour (Down HS), A Craig (Instonians), K Greene (St Mary's College RFC).
Referee: M Stanish(New Zealand).
