Latvia know it, Germany know it, Spain know it and England certainly know it - one goal is not enough to win or sometimes even draw a game at Euro 2004.
Spain dominated their match with Greece at the Bessa Stadium, controlling possession and territory with relative comfort throughout the match but one deadly finish from Angelos Charisteas meant they finished with just a point.
Had Raul put away one of the chances he was given then Spain could already have their feet up with qualification for the quarter-finals secured.
But their inability to find a second goal meant despite restricting Greece to long-distance shots for all but one crucial moment of the game, Spain face early elimination should they get beaten by Portugal and Otto Rehhagel's men pick up just a point against a blunt-looking Russia.
So far only one team has won 1-0, and that is Spain who thanks to Juan Carlos Valeron's goal held on to beat Russia in the second game of the tournament.
By then Greece had already beaten Portugal, who having built up a-two goal cushion could afford to concede a late header from Cristiano Ronaldo.
Latvia couldn't hold onto their narrow lead against the Czech Republic and slipped to defeat while enough has already been said about the last three minutes of England's game with France.
On Tuesday, Germany were denied an opening Group D victory thanks to Ruud van Nistelrooy's classy near-post finish.
Some may feel it is a lack of bottle on the part of the teams who have let leads slip and in the 2002 World Cup, where the same thing happened on plenty of occasions, it was.
That may also be true in Portugal but what is glaringly obvious in Euro 2004 is one goal is not enough because of the fantastic talent of the players on show.
England did make errors but would a free-kick from 20 yards out have been so consummately dispatched at such a crucial period of the game by anyone other than one of the top players in the world, in this case Zinidine Zidane?
On Wednesday, Spain found that just a minor slip can be cruelly punished as Charisteas slammed home what was barely a half-chance when a long ball was sent his way.
Van Nistelrooy's effort against Germany was perhaps the perfect example, the Manchester United striker still produced an unstoppable finish despite being manhandled by Christian Worns as he hooked the ball home.
Dietmar Hamann summed up my point neatly when he commented: "Our two centre-halves are very experienced and they had barely given him a chance all game, but then I know from seeing so much of him that he only needs that one chance to change a game."
The German was talking about Van Nistelrooy but he may as well have been talking about all of Europe's top players at Euro 2004.