Coleraine rower Peter Chambers has been ruled out of the Lucerne World Cup regatta because of injury.
Chambers and his brother Richard were part of the British lightweight four which won silver at the opening World Cup meeting in Belgrade.
However, Peter's injury means that 2010 world champion Paul Mattick returns to the British boat.
Alan Campbell will compete for Britain in the singles sculls in Lucerne after finishing second in Belgrade.
Campbell won world championship bronze in 2011 and is regarded as a strong medal contender for the London Games.
Peter Chambers has broken into the Olympic-class boat after winning world titles at Under-23 and senior level in the non-Olympic class lightweight men's pair last year with Newcastle's Kieren Emery.