South African winger Bryan Habana equalled Jonah Lomu's record of 15 Rugby World Cup tries with a hat-trick in the Springboks' 64-0 demolition of the US to seal their place in the quarter-finals as pool winners.
The former world champions would not have expected to have so much riding on their final group match against the bottom team in Pool B, but their humiliating opening defeat to Japan had left them needing a win to shut the door on Scotland and the Japanese.
After leading only 14-0 at halftime, initially struggling with the slippery conditions, the South Africans ran in eight second-half tries, including Habana's 20-minute hat-trick, to set up a quarter-final against either Australia or Wales.
"We came to the game and knew we had something to prove, and it's exciting now to be going to the quarter-finals," man-of-the-match Damian de Allende said in a pitchside interview.
Ten tries did not look on the cards in a scrappy first half at London's Olympic Stadium, though centre De Allende gave a glimpse of what was to come when he ghosted through the Eagles' inexperienced defence to score his first international try.
The United States, who made 12 changes from the team that led Scotland for 40 minutes before running out of steam, kept the margin in single digits for almost half an hour before submitting to the Springbok scrum and conceding a penalty try.
They did briefly get U.S. fans on their feet when fullback Blaine Scully intercepted with the length of the field ahead of him, only to turn inside to be wrapped up by the South African defence.
It took exactly one minute of the second half for Habana to open his account, racing on to a perfectly timed Fourie du Preez kick to swallow dive over the line.
South Africa's pack, loaded with far too much power for the United States, took over and hooker Bismarck du Plessis and flanker Francois Louw barrelled across the line before Habana completed his hat-trick to a standing ovation.
The 1995 and 2007 winners, who had erred on the side of caution by making only two changes from Saturday's win over Scotland, were running riot by this time.
The widest margin of victory in the tournament so far was wrapped up with further tries from Jesse Kriel, Lwazi Mvovo and Louw, with Habana only a knock-on away from making the try-scoring record all his own.