Such is Henman's new self-belief that the man who only last week ruled out his French Open chances said after beating Puerta: "If I can play in these conditions, I can play anywhere."
The Briton went a break down in the first set after losing the sixth game, but hit back with two successive breaks to take the initiative. He swept through the second set as his 20-year-old opponent tired, completing the victory in one hour 16 minutes and setting up a last eight meeting with either Spain's Francisco Clavet or another Argentinian, Mariano Zabaleta.
Henman, who won 82 per cent of points on his own serve, said: "My level has improved in the last two weeks and my confidence has been growing. There's been a huge improvement for me on clay this year. I feel like I've really got my teeth into it."
Tommy Haas became the only German to advance to the quarter-finals when he rallied to beat Greg Rusedski's second-round conqueror, Alberto Berasategui, 3-6, 6-1, 6-4.
Carlos Moya advanced to the last eight by beating Adrian Voinea 7-5, 7-6. Moya remains the only contender with a chance to dislodge Yevgeny Kafelnikov from the No 1 spot. The Spaniard, who already held the top ranking for two weeks in March, needs to win the tournament to end Kafelnikov's reign after only one week.
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