Andy Murray came from two sets to one down to earn a thrilling 6-3 3-6 2-6 6-3 6-2 win over Fernando Gonzalez in the third round of the US Open.
Murray will face seventh seed Nikolay Davydenko next
Murray began nervously, losing his opening service game, but soon found his form to take the first set.
The Chilean then unleashed his vicious forehand and looked headed for victory as he took the next two sets.
But Murray lifted himself to snatch the fourth set, and two breaks at the start of the fifth set him up for victory.
"I just kept fighting," said Murray.
"He's so difficult to play against. He slices every backhand and then as soon as he gets a chance on a forehand he hits it really hard so it's difficult to get into a rhythm against him.
"But when you're playing best of five sets you have to hang in until the end."
Twenty minutes before I went on, I saw Agassi play his last match and I was genuinely upset
Murray will face seventh seed Nikolay Davydenko in the last 16 after the Russian thrashed Lukasz Kubot of Poland.
"I'm looking forward to it," added Murray. "I think I showed today that I'm getting physically stronger and I'm playing the best tennis of my life."
The 19-year-old is right to be confident after beating 10th seed Gonzalez from a seemingly doomed position.
In a see-saw first set, Murray broke Gonzalez's serve three times but he did not have another break point until the eighth game of the fourth set.
The Chilean, combining a degree of guile with his devastating power, looked in complete control as he cruised into a two sets to one lead.
But Murray proved he has added match toughness to his undoubted talent.
He stuck with Gonzalez in the fourth set and then found a series of magnificent returns to break at 4-3.
He carried the momentum into the fifth set and at 5-1 had to keep his composure as a storm erupted at the other end of the court.
Gonzalez, who had already been warned for breaking his racket in the previous game, was docked a point for smashing a ball out of the stadium and had several long arguments with the umpire as the crowd voiced their support for the Chilean.
However, it failed to unnerve Murray, who served out a bold victory to love.