Roddick will play Rafael Nadal today at noon at Arthur Ashe stadium.
Roddick, the No. 21 seed in the tournament, got out to an early lead, taking the first two sets 6-3, 6-4. But he dropped the third set to Ferrer 6-3, setting up a dramatic fourth set.
Roddick and Ferrer went back and forth holding service until the fifth game, when Ferrer went up 15-40 quickly. Roddick would eventually force deuce, but end up losing the game, giving Ferrer a 3-2 advantage.
But he lead wouldn't last long. After again falling behind 15-40, Roddick again forced deuce, but this time broke Ferrer serve and tied the set at 3-3. Roddick would win the next three games to take the match.
Visibly relieved following his victory, Roddick circled the small Court 13 giving high-fives to a crowd that was overwhelmingly in favor of the American.
The match was moved to the smaller court from Louis Armstrong Stadium, as a riled Roddick refused to take the court. After two days of nearly non-stop rain, water was seeping up from under the court, leaving wet spots. Roddick refused to play on the court.
"All courts were dried prior to play," read a statement issued by the USTA. "However, as the sun began to warm, or "bake" the courts, evaporation of these saturated conditions began to surface on Louis Armstrong Stadium."
Roddick is one of two Americans left in the tournament. The other is No. 28-seed John Isner, who will face No. 4-seed Andy Murray of Great Britain, also today.