Men's single sculls quarterfinals of 2016 Olympic rowing regatta took place on Tuesday when 2012 Olympic champion Mahe Drysdale from New Zealand beat runner-up Ondrej Synek from the Czech Republic in the second quarters, a replay of the finals in the London Games.

Drysdale finished the race in 6 minutes and 46.51 seconds, four seconds ahead of Synek. Both athletes went through to the semis.

"Whenever you meet Ondrej it's a battle and it's hard when you meet each other so early. You can see Ondrej didn't go the full distance, but we'll see what everyone's got when we hit the later stages," said Drysdale.

"It's nice to get the quarterfinals out of the way. There's not much to gain but everything to lose," he added.

Synek had expected the result of the race as he knew Drysdale isn't a person who wants to lose a race.

Tuesday's action also featured the quarterfinals of women's single sculls, the semifinals of the men's and women's double sculls, the men's pairs and the lightweight men's fours.

In the women's double sculls, world champions Eve Macfarlane/Zoe Stevenson from New Zealand missed out on a A-final place for failing to squeeze into top three of their group.

Olympic lightweight men's double sculls champions Rasmus Quist/Mads Rasmussen from Denmark won the repechage to reach the semis.

"It was a little rollercoaster being there, not being there, and then being there again. We're very lucky to be here and we're very happy to be here. We really want to deserve to be here. The plan is to come back and defend the gold (won in London 2012)," said Quist.

"We've had a hard time coming back, especially last year, being hit by injury and sickness and that kind of threw us six to nine months back in training. Yesterday it didn't quite work for us and we were maybe a little bit too eager to get going. We took the gas off a little bit in the last 500m yesterday and again today," Quist added.

But lightweight women's double sculls champion Katherine Copeland from Britain will have no chance to defend her title. Copeland and partner Charlotte Taylor finished third in their repechage, and will race again on Wednesday for a place in the C-final.