When Phelps jumped into the pool for the third leg of the 4x100-meter medley relay on Saturday night, the Americans were just behind Great Britain in second place.
In Rio, where he took his Olympic tally to a staggering 28 medals - he also won three silvers and two bronze - it was apparent he was not going through the motions at all.
In the latest embarrassment to the Southern Hemisphere's first Olympics, the U.S. Olympic Committee said Ryan Lochte and three other American swimmers were robbed by armed men who stopped their taxi hours after the final night of swimming.
Nathan Adrian made no mistake on the freestlye leg and ensured the 31-year-old Phelps finished with a gold in what was the final event of the swimming program in Rio.
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The defending champion, who is trying to become the first player to win two Olympic singles golds, faces Juan Martin del Potro of Argentina in the men's final Sunday in Rio de Janeiro.
"He doesn't need this, his legacy is going nowhere, which makes this more wonderful", he said.
The younger generations reading this won't yet fully understand how the retirement of an Olympian whose ups, many ups, and downs you have followed for such a large slice of life, through five Olympics, feels like the onset of grey hair, the wrong side of a watershed.
"This all started and began with one little dream as a kid that changed the sport of swimming and tried to do something nobody else has ever done", said Phelps.
"I was thinking about that today", added Phelps, who now intends to spend more time with fiance Nicole and newborn son Boomer. "The point is to go out there and be the best athlete you can be", American teammate Dagmara Wozniak said.
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Michael Phelps left the Olympic pool for the last time on Saturday having fulfilled a childhood dream, but it is clear he will not be walking away from the sport that has turned him into a global household name.
"So I think I have the wedding in order, and now it's on to the party for the fun", she added.
He already has those gold medals from Beijing in 2008 and London 2012, but can he repeat the feat at Rio? While some Olympic historians have disputed the number of golds the USA has won, the United States Olympic Committee said that the women's victory would count as the country's 1000th.
Britain took silver, thanks largely to a breaststroke leg from Peaty that was quicker than the world record he set to win individual gold, but won't count as it came in the middle of a relay. "We were just kind of staking our claim in Rio, and I think we kind of did that in the pool as well".
The U.S. Swim Team so far has won a staggering 33 Olympic medals this year, including a total 16 gold medals, eight silver, and nine bronze.
"We came together as a team and Michael was like 'You know guys, I don't really have anything to say".
"That's something I've been going for for a long time", said Murphy. She took silver in the women's 50 freestyle and then anchored as the USA women won the 4x100 medley.
Connor Jaeger of the USA took the silver, and Italy's Gabriele Detti won bronze after overhauling Jordan Wilimovsky of the U.S.in the closing stages.
Blume finished in a time of 24.07 seconds ahead of Manuel (24.09) and Aliaksandra Herasimenia of Belarus (24.11) to win Denmark's first swimming gold since 1948.
The 22-year-old Puig defied her ranking of 34 to get the better of the world number two and Australian Open champion on the back of 54 winners.
