Rob Smedley says maintaining third spot is the minimum Williams should be aiming for in 2016, but admits they are looking over their shoulders.
A dramatic turnaround in fortunes under new regulations introduced at the start of 2014, has seen Williams leap from ninth in the constructors' championship in 2013, to third in each of the last two seasons.
"We don't want to be hanging onto third, third has to be the minimum of targets really this year. The team is moving forward all the time, third and upwards is what we are aiming for now," Smedley, Head of Vehicle Performance, told Sky Sports News HQ.
However, Williams maintaining third spot last year owed much to Red Bull's catastrophic campaign as the Grove team were overhauled by Ferrari and Smedley is expecting pressure from behind in 2016.
"I think Force India were making great strides at the end of the year," he added.
"Red Bull - it would be really silly to not consider them as being a really strong outfit, with a good engine they can start to move forward.
"The works Renault team are going to have that engine now and they are going to start investing. So I think there are lots of people behind us who can make great strides."
Former Williams driver turned Sky Sports F1 pundit Damon Hill suggested his old team could never hope to beat Mercedes with a customer engine supply. But Smedley disagrees with the 1996 world champion that Williams would be better off with a different power unit.
"First of all we are really, really happy with the level of service and the power unit itself we get from MHPP [Merceces High Performance Powertrains]," he said.
"There was a small difference in performance late in the season between ourselves and the works team, but that is not normal.
"There is only a finite amount of engines that can be supplied, that is one of the reasons. But I think ultimately we are really happy, they are a very professional outfit and they supply an incredible power unit as well."
Indeed, Smedley doesn't believe teaming up with an engine manufacturer to become a works team is currently the right direction for Williams.
"I don't think it is the obvious next step, I don't think that we have exploited anywhere near what we can do as a privateer team," he said.
"I think we are a percentage, be that 30 per cent, 40 per cent or 50 per cent towards restructuring the team and to exploiting it to its maximum potential.
"So before thinking about a full restructure again I think we have to think about the restructure that we are in the middle of now, still as a privateer team and to exploit that current structure to 100 per cent."