Great Britain missed a chance to set crews for Olympic year as illness and injury hit final trials in Belgium.
Sarah Winckless, Annie Vernon and Fran Houghton, all in the hunt for places in the quad, were all ruled out.
And Matt Langridge had to withdraw from the men's pairs trial, leaving partner Steve Williams on the bank too.
Andy Hodge and Peter Reed won for the fourth successive year while Katherine Grainger picked up her seventh trials title - this time in a single scull.
Great Britain head coach Jurgen Grobler will aim to set his crews for the season by the end of March, with the first of three World Cup events starting in Munich on 8 May.
He must decide whether to stick with the coxless four line-up of Hodge, Reed, Williams and Alex Partridge, which finished a disappointing fourth at last year's World Championships.
Partridge, rowing with Rick Egington, finished third behind World Championships bronze medallists Colin Smith and Tom James in Saturday's pairs trial.
The women's quad won their third successive world title last September with a crew including Houghton, Grainger and Debbie Flood, who finished behind her in the trials final.
Vernon, who moved into the quad last year when Winckless was injured, was faster than Grainger in the semi-finals earlier on Saturday before pulling out with a virus.
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