Hamish Bond and Eric Murray are unbeaten in 66 successive races since being paired together following the 2008 Beijing Games and are heavy favourites to win a second Olympic gold at the Rodrigo de Freitas lagoon.
"In terms of an outside view, I guess it's a given," Bond told Reuters. "We have won 60-something races in a row and it doesn't take a rocket scientist to put pretty short odds on us winning the next race.
"Having said that, you're only as good as your last race."
The U.S. women's eight have enjoyed an even more impressive period of dominance under coach Tom Terhaar having been unbeaten in every major race since 2006.
Only two of their London 2012 gold medal-winning crew, Meghan Musnicki and Eleanor Logan, however, have returned for Rio and they could be pushed by the fast-emerging New Zealand team, the British, Dutch and Canadian crews.
Britain, who topped the medal table in rowing at the London Games with four golds and nine medals overall, have qualified 12 out of a possible 14 boats for Rio.
They are likely to be pushed hardest by New Zealand, who showed strong form at last month's final World Cup event in Poland with all 10 of their then Rio qualified boats winning medals, five gold, as they won the overall 2016 trophy.
New Zealand earned an 11th spot earlier this month when Russia's Sergej Fedorovtsev tested positive for the banned substance trimetazidine, which resulted in their men's quadruple scull being disqualified.
Several veterans could also be making their swansongs in Rio, with twice women's single sculls champion Ekaterina Karsten of Belarus qualifying for her seventh Games at the age of 44.
Norway's twice single sculls champion Olaf Tufte will compete in his sixth Games, although the 40-year-old will be in the men's double sculls with Kjetil Borch.
The decision by international body FISA to ban all but six Russian rowers for the Games also saw a mad scramble for reallocated spots earlier this week.
Australia's women's eight, Italy's men's eight, Greece's men's lightweight four and Italy's women's lightweight double scull all got late entries for the Aug. 6-13 Rio competition.
(Editing by Ken Ferris)
