The 31-year-old had a difficult build-up to his home race as he was still nursing injuries following his crash at Imola a fortnight ago and he needed a late fitness test before being cleared to take part in the event.
The Red Devils Aprilia rider went on to claim to fourth places on Sunday, but he admits he was feeling the effects of his injuries late in both races.
"I'm fairly pleased with the results considering my conditions," he said.
"Obviously I would have liked to have been on the podium for my fans, but I think that in the end two fourth places are the most we could have aimed for. I started well in both races and then I started feeling the fatigue."
Haslam remained second in the Riders' standings behind Jonathan Rea, but Tom Sykes on the other Kawasaki is now just one point behind him following his two P1s at Donington Park.
"In spite of it all, even here we showed that we are in the game," Haslam added.