World champion Anna Watkins will not join her title-winning partner Katherine Grainger at the season's first World Cup event in Munich.
Watkins has a back injury and has been replaced by Mel Wilson in the women's double scull.
"It was better to play safe," said performance director David Tanner.
"We wanted to be sure that Anna was ready to race next month and we expect that she will be back in time for Hamburg in the middle of June."
Watkins and Grainger were crowned world champions and named International Rowing Federation crew of the year after an unbeaten season in 2010.
Britain have also added a second boat in the lightweight women's double scull, the lightweight men's four and the lightweight men's pair.
Tanner has taken the move to assist Britain's preparations for both the Under-23 World Championships in June and the senior World Championships in September, which doubles up as an Olympic qualification regatta.
The second lightweight men's four contains three of last year's under-23 world champions in Jamie Kirkwood, Jono Clegg and Will Fletcher.
The second lightweight men's double contains 2010 world silver medallists Kieren Emery and Peter Chambers.