Spain v Portugal: In a column written this week for Italian daily, Corriere Della Sera, Portuguese playmaker Rui Costa candidly admits that both Portugal and Spain had hoped to arrive at this third Group A qualifier with a foot already in the quarter-finals.

Alas for Spain and Portugal but to the great delight of neutrals, things have not panned out that way and this traditionally intense derby between two great rivals and neighbours has become a desperate "do-or-die" affair.

As always at this stage, the mathematics offer a variety of permutations but, in essence, the bottom line is simple enough. For Portugal, only a win will guarantee a place in the quarter-finals whilst for Spain a draw will suffice.

Rui Costa, dropped at half-time in Portugal's opening 2-1 defeat by Greece and replaced by the in-form Porto playmaker Deco, believes his team's 2-0 win over Russia on Wednesday night has put the host nation's campaign back on track.

He argues, and few would disagree with him, that Portugal's problem against Greece was nervousness, induced by the pressure of the nation's expectations: "The side that lost against Greece wasn't the real Portugal. Against Russia, we refound our true game, regardless of who is in the side. Our national team, after all, is characterised by good ball control and ambitious individual talents. Against Greece, the thing that did us in was nervousness," says Costa, who himself seems certain to again start on the bench, notwithstanding his late goal against Russia after coming on as a second-half substitute.

In truth, Portugal's problems in that opening game appeared to be caused by more that just nerves. Rui Costa himself in the playmaker role, Fernando Couto in central defence and full backs Paulo Ferreira and Rui Jorge all seemed slow and ponderous. All four were dropped against Russia, with their replacements - Deco, Ricardo Carvalho, Nuno Valente and Miguel Monteiro - adding pace, invention and drive.

Having rung the changes for the game with Russia, Luiz Scolari is now unlikely to to make further switches, almost certainly opting to stick with the side that started against Russia.

As always with this Portuguese side, much will depend upon the team's captain and most charismatic figure, Real Madrid's Luis Figo. In both games so far, Figo has appeared to try too hard, as if determined not only to justify his status of national idol but also as if convinced that he could, single-handedly, pilot Portugal to victory.

A little more altruism and a little less selfishness, not to mention a willingness to link more with Deco, could serve the Portuguese well. In attack, too, Pauleta, whose goalscoring touch has thus far deserted him at this tournament, is under pressure from Benfica striker Nuno Gomes.

For Scolari's opposite number, Inaki Saez, the game poses some difficult questions. His side have been less than impressive in a 1-0 win over Russia and a 1-1 draw with Greece. Most worrying for Spain has been the apparent poor form of team captain and talisman Raul Gonzales, who compounded a miserable showing against Greece by missing a relatively straightforward header that would have wrapped up the match when it was 1-0 in Spain's favour.

Does Saez acknowledge the evidence of the last two games and commit virtual heresy by dropping Spain's most famous footballing son? Likewise, does he ignore the current good form and goalscoring touch of Monaco striker Fernando Morientes in favour of the more dynamic Atletico Madrid striker Fernando Torres? Should the exciting Joaquin not start ahead of Joseba Etxeberria?

In all probability, Saez will stick with Raul, Morientes and Etxeberria opting, as against Russia and Greece, to replace them with Deportivo's Juan Carlos Valeron, Torres and Joaquin in the second half. Saez will, however, have to reshuffle his defence since central defender Carlos Marchena is suspended, due to be replaced by either Juanito Gutierrez or Cesar Martin.

In what is arguably the biggest game of the tournament so far, both sides will be under fierce pressure. Spanish striker Torres, however, believes that the pressure cooker situation could work against Portugal and in favour of Spain, saying: "It would be a failure for us if we were eliminated on Sunday. Spain have to be in the quarter-finals. Yes, we are under pressure but most of the pressure is on them since we only need a draw and they are playing at home."

PROBABLE LINE-UPS

PORTUGAL (4-2-3-1): Ricardo; Nuno Valente, Carvalho, Andrade, Miguel; Maniche, Costinho; Figo, Deco, Simao; Pauleta.

SPAIN (4-2-3-1): Casillas; Puyol, Helguerra, Juanito Gutierrez, Raul Bravo; Albelda, Baraja; Etxeberria, Raul, Vicente; Morientes.