Lopez had other ideas and hit back to win the next two sets in tiebreaks after all games went with serve.

He reeled off the first tiebreak 7-2 and, in the second, came back from 4-2 behind to win four points in a row and clinch the breaker 7-4 with an ace.

With the crowd at the Polideportivo Malvinas arena increasingly quiet, Lopez continued his dominance by breaking in the fourth game of the fourth set, helped by two Del Potro double faults, to take control.

Already looking fatigued after a long season that has seen him leap from obscurity into the top 10, Del Potro managed to break back immediately but then suffered his injury in the next game.

He soldiered on but Lopez wrapped up the match comfortably. Argentina, unbeaten at home in 10 years, went into the final as firm favourites to win the competition for the first time against opponents missing injured world number one Rafael Nadal.

The first match went according to the script as Nalbandian thumped Ferrer 6-3 6-2 6-3 in one hour 59 minutes to give the hosts the perfect start.

"I played well from start to finish, I was always in control of the situation and the public was incredible," said Nalbandian. Ferrer was dejected.

"I felt inferior," he said. "David was far superior and there's nothing more to say."

Sanchez supported his number one player. "He was up against one of the best in the world on this surface and I don't think he was so bad."