Second-half goals by Walter Ayovi and Pablo Palacios gave Ecuador a crucial 2-0 win over Argentina and kept them in the hunt for a place in the 2010 World Cup in South Africa.
Ecuador`s Argentinian-born goalkeeper Marcelo Elizaga was the man of the match after saving a Carlos Tevez penalty plus a host of other crucial shots during the match before Ayovi and Palacios secured the victory.
The hosts also had to make do without Carlos Tenorio from the 13th minute, when he was replaced with Jefferson Montero due to a back injury, a change Argentina tried to take advantage of.
In the 11th minute, Messi failed to connect with a Gabriel Heinze cross from the left while under pressure from Elizaga, then 17 minutes later Argentina had their best opportunity to open the scoring as Elizaga fouled Tevez just after the Manchester United striker entered the box.
Elizaga saved the resulting penalty before Messi shot the rebound over the bar.
Wigan winger Antonio Valencia had Ecuador`s first chance after 31 minutes when his shot from long distance went slightly wide.
But Argentina maintained the upper-hand, with Elizaga showing himself to be the best player on the field on the night again by saving a double chance for Argentina, firstly by stopping Heinze`s shot from the left before keeping out the rebound from Fernando Gago.
But then with 18 minutes to go Ayovi surprised Argentina keeper Mariano Andujar with a long-distance shot from the left that sailed just under the bar.
Then in the 83rd minute Martin Demichelis failed to clear the ball and Palacios was their to steal the ball and steer it into the net.
The defeat leaves Argentina fourth in the group, but Ecuador are now just two points behind.
Argentina coach Diego Maradona was left to regret the chances his side wasted, but insisted he had little else to regret.
"We put our faith in the counter-attacks with fast players like Tevez, Messi, Jonas Gutierrez and Maxi Rodriguez. I think the tactics were good," he said.
"We did everything to win. We missed a penalty, at least three one-on-one chances. This is football: when you miss chances then you suffer.
"We were unlucky, but we have to be patient. This team is improving and today in the dressing room we all promised to beat Brazil at home in the next round."
Tevez also had few regrets about his missed penalty.
"It was down to (goalkeeper) Elizaga. He made a great save," he said.
"The result was totally unfair. We played well, we created chances but we couldn't score and now we must to think about the key match against Brazil."
Ecuadorian coach Sixto Vizuete was excited by the triumph, saying: "We obtained three golden points.
"A few months ago, against Brazil, we created a lot of chances and only scored a late goal. Today we took advantage of the two or three we had.
"If we get good results in the next two games against Colombia and Bolivia will be very close to going to South Africa."
Argentina meet Brazil in Buenos Aires on September 5, while Ecuador visit Colombia.