Alastair Seeley is now 34 points behind British Supersport leader Stuart Easton after failing to make the podium in this weekend's races at Assen.
The Carrickfergus rider finished fourth in Saturday's sprint race before coming fifth in Sunday's feature race.
Easton won both races to increase his lead ahead of the final two rounds at Silverstone and Brands Hatch.
Glenn Irwin was seventh and 12th while Marty Nutt had two third-place finishes in the Ducati 848 Challenge.
Seeley came in 1.92 seconds behind Seeley in Sunday's race with Jason O'Halloran second and Ben Wilson in third.
Richard Cooper was second in Saturday's sprint with O'Halloran completing the podium.
"That was a good weekend, we had a good pace all of the way through," Scotsman Easton told the BSB website.
"The double win and in the second race leading from start to finish was a good result so it's fair to say that we have been quite dominant.
"Now we have to keep focussed, working hard to continue like this into Silverstone, keeping the pressure up on Alastair."