By Tom Fordyce BBC Sport Online

How long can David Seaman go on as England's goalkeeper?

Seaman won his 75th cap against Macedonia on Wednesday, a month into his 40th year.

By the time the 2004 European Championships come round, he will be 41 years old.

Eriksson's decision is fundamental to England's future

And that means England coach Sven-Goran Eriksson had a big decision to make this week even before Seaman's costly blunder against Macedonia.

Does he believe Seaman can maintain his form and fitness at the level required for another 19 months?

If not, when does he end Seaman's international career?

The media clamour is for Eriksson to wield the axe now.

But there are two precedents for manager and goalkeeper to consider.

Dino Zoff was 40 when he captained Italy to their World Cup triumph of 1982.

Although protected by the magnificent Gaetano Scirea and Giuseppe Bergomi in front of him, not to mention iron-man Claudio Gentile in midfield, Zoff's performances made his age a non-issue.

He actually had a better tournament than in Argentina four years previously, aged 36, when Arie Haan's swerving 40-yarder flew past him and cost Italy a semi-final place.

Obsessive trainer

Then there is Peter Shilton, 40 years old when England went to the 1990 World Cup finals.

Shilton was faultless in the World Cup semi against West Germany

Shilton did not make any errors as England went out in the semi-finals to West Germany, even guessing the right way on each penalty in the shoot-out - although, admittedly, he failed to save any.

Only in the third-fourth place play-off did he begin to look his age, caught dwelling on the ball as Roberto Baggio put Italy level before Toto Schillaci's late winner.

Shilton was an obsessive trainer, a man so dedicated to his craft that he was still playing professionally aged 47.

Seaman, another man who prides himself on his fitness, believes he is in good enough physical shape to keep going.

But he has suffered more injuries in recent years than either Shilton or Zoff endured, and these will slow him down.

The specialist nature of the keeper's position makes Eriksson's decision still harder to make.

Eriksson is an astute coach who understands what is required by players at the top level.

It may have appeared obvious against Brazil and Macedonia, but to be able to judge when Seaman's reflexes, positioning or decision-making begin to slip requires the insider's knowledge that only another keeper could bring.

Seaman works on his reflexes with England

Seaman's form, if it does deteriorate, will not collapse. The change will be marginal - enough to prove crucial at international level, but too minor for an outfield coach to spot in training.

It might manifest itself as a reluctance to come for a cross - not a mistake as such, but a failure to prevent a possible goal-scoring opportunity arising in the first place.

Even taking Wednesday's blunder into account, there are many who believe Seaman is still the best man for the job.

But if Eriksson feels that will change by the finals of Euro 2004, he needs to blood the alternatives soon.

Not one of Seaman's rivals for the number one jersey has played a single competitive game for England.

David James has 10 caps, all of them in friendlies. Paul Robinson has yet to make his senior England debut.

Seaman was safe for last weekend's games against Slovakia and Macedonia.

But his blunder at St Mary's on Wednesday may just hasten the ageing process.