Massa said that Ferrari put together all their new components at Spa and was encouraged at how much better the car felt.
"I think we still need to keep working - put new parts on the car and try to make the car more competitive," Autosport quotes Massa as saying. "We missed some opportunities and some races where the bits were not working, and we lost a little bit of time.
"But with the car [in Belgium], everything we brought we were using – so I hope we can carry on in this direction. If we do that the car will be better.
"From now to the end of the races, we can be more competitive than we were in the first part of the season."
Ferrari are currently third in the constructors' championship.