Doing all three would have left little time to work on specifics in between and Walker doesn't necessarily put major emphasis on Carrington's performances at those regattas.
"We've got a training block planned between now and Rio and whatever happens at these World Cup won't change that.
"Testing ourselves at these World Cups is helpful to a degree but it's more important that internally we know what we're doing and we're confident we know where we're going on a day-to-day basis.
"It's really about being in the best shape you can, once per year, and what it's going to take to do that is probably our biggest consideration."
Carrington was headed in the longer distance by returning Hungarian star Danuta Kozak, a multi-medalled champion paddler now back in the single seat after time away in multi-seat disciplines.
That result gave Carrington a good indication of how much work she'll need to do to pull off her ambitious double gold objective in Rio.
"We always knew that Danuta would be back. She's obviously a very good athlete.
"[Duisburg] was an opportunity for Lisa to race her and Inna [Osypenko-Rodomska of Azerbaijan], who is another great challenger. But being beaten by Danuta hasn't really changed anything."
Carrington and training partner Marty McDowell, who is contesting the K1 1000m in Rio, have been in Berlin for the past few days before heading to Portugal.
McDowell has been battling illness but is expected to be ready to race at the weekend.
This weekend will be Carrington's last significant event before the Games.
