With only one crew qualifying directly to the final, two of the event's top boats will find themselves in the repechage and therefore having to compete in an extra race in their bid for gold.
Germany, which is unbeaten in three years, is the world champion, while Canada is the reigning Olympic champion. Britain is a dark horse for gold on home territory.
The United States and Australia are the standout crews in the other four-boat heat following Thursday's draw for all the heats in the regatta.
Four countries will advance from Monday's repechage for a six-team final on Wednesday.
Canada and U.S. — the two favourites — have been kept apart for Sunday's heats for the seven-team women's eight. Britain and Australia will also compete in different heats in the men's four on Monday.
Saturday's men's single sculls contains 33 competitors — the biggest contingent for any event — across six heats.