I think that's a fair way to say it: "Nalbandian lost a shade of concentration in the third set breaker...." It wasn't like he completely choked. Still, you get up in that breaker, 2 points from a 2 to 1 set lead, you must close it there. From Spain's perspective it was good they had Lopez serving at 2-5 in the breaker. He hit the service winner wide, if I remember right, and held those two points to get to 4-5 so that put them right back in it.
The fourth set, it looked like Argentina lose a little bit of self belief. I could be mistaken, but it often looks like when Nalbandian gets a little tight on serve the toss is a little lower and he likes to go down the middle (over the low part of the net). He barely missed that down the T serve a few times in the third and fouth sets.
I agree with LendlFan in saying Spain rose. The F-Lo win over del Potro was obviously immense because then it sets up Saturday with F-Lo/Verdasco, who are friends and had played 6 doubles matches in a row in Davis Cup, vs. Nal/Calleri, who are both obviously good players who had played together, but not nearly as much as the two Spaniards.
Spain outplayed them and deserved it. From the Argentine side there are obviously going to be questions starting with the selection of the site in Mar del Plata, which the players - especially Nalbandian who wanted to play in Cordoba - did not feel was the right choice.
It's unfortunate that the schedule continues to play a role - how much of a role is debatable - but when you have the first Davis Cup final in history between two Spanish speaking nations and the World No. 1 does not play, when you have the #9 player in the world unable to play a critical match on the last day of singles play, etc. that's an issue. And I know people say injuries are a part of sport, which is true, but the Davis Cup final will always be more vulnerable to these kinds of occurrences as longa s the ITF sticks to an antiquated format. And I'm not arguing it would have altered the outcome, I'm simply saying when you have an event as important as this one there is no excuse not to have the best players playing in the best health possible.