Benfica's pitch was under water last night and the Republic, who need to beat Portugal to ensure qualification for next summer's finals in England, could not have their final training session on the ground.
Sean Connolly, chief executive of the Football Association of Ireland, said: "More rain is forecast for tomorrow and if the pitch is in the same condition as it is tonight there's no chance of the game going on. We have had no official word from the Portuguese FA so far, but our plan is to go to the stadium again early tomorrow morning and see how things stand."
A postponement would have repercussions in Belfast, where Northern Ireland are due to play Austria tonight in a match that also has a profound bearing on the Republic's position. The governing body of European football, Uefa, has ordered that both matches kick off at the same time so there can be no opportunity for complicity over the results.
The Republic are one point ahead of third-placed Austria in Group Six and must match Austria's result against Northern Ireland to secure second place and a possible play-off at Liverpool.
Connolly has warned the Portuguese FA that the Republic will not accept a switch of venue, which is thought to be under consideration by the home country.
Sporting Lisbon's stadium is only a few miles away from Benfica's and has better drainage facilities, but Connolly believes a late switch could cause chaos among the fans. An estimated 20,000 have travelled to Portugal and Connolly said: "I would think 80 per cent of them do not know there is a problem and they are coming from all parts of Europe as well as America and, of course, Ireland.
Any delay in the match could help Andy Townsend in his race to be fit. Yesterday Jack Charlton, the Republic's manager, had appeared to be on the point of ruling him out because of a foot injury. Townsend was unable to pass a fitness test despite a course of injections to ease the pain in his instep.
Townsend's absence would give Charlton a complicated selection problem. Steve Staunton, who has had hamstring trouble, has been declared fit for his familiar role on the left side of midfield, but with Roy Keane absent after a hernia operation, Charlton needs security at the base of midfield. Blackburn's Jeff Kenna was not a great success in that role against Latvia last month.
"I've still quite a few options and may bring Phil Babb out of the back four to play in front of them, and put Alan Kernaghan in there," Charlton said. "We've managed without Roy before."
In fact, Keane has played in only three of the other 11 qualifying matches, but Charlton said: "When you are also missing Andy from that area it becomes very difficult for us.
"We are not the team we were. We used to have a phenomenal work-rate and always said the most important thing was what we did, not the opposition. But some of the players are getting a bit long in the tooth now and others are inexperienced. We'll see."
The Republic produced their best performance for some time when beating Portugal, the group leaders, 1-0 in Dublin in April and a repeat tonight will put them into the finals as group winners.
Failure to qualify for the finals would cost the Republic's players around pounds 50,000 per man in bonus payments. The country's Football Association would also have to forgo an estimated pounds 5m if they did not reach the finals.
However, the biggest loss could be the departure of Charlton, who is expected to resign if the Republic fail to qualify, even though he now insists he will not immediately walk away if the result goes against him. If so, it would bring to an end a glorious era in Irish football.
PORTUGAL (European Championship Group Six v Republic of Ireland, Lisbon, tonight) (Probable): Vitor Baia; Secretario (both Porto), Fernando Couto (Parma), Helder (Benfica), Paulinho Santos (Porto), Paulo Sousa (Juventus) Oceano (Sporting Lisbon), Figo (Barcelona); Joao V Pinto (Benfica), Rui Costa (Fiorentina), Domingos (Porto).
REPUBLIC OF IRELAND (Probable): A Kelly (Sheffield Utd); G Kelly (Leeds), Babb (Liverpool), McGrath (Aston Villa), Irwin (Manchester Utd); Houghton (Crystal Palace), McAteer (Liverpool), Kenna (Blackburn), Staunton (Aston Villa); Quinn (Manchester City), Aldridge (Tranmere).Reuse content