"It's the best we could do," the Red Bull driver is quoted by Italy's Autosprint.
"Obviously we have to improve in many areas, including the power unit."
Indeed, so far in 2015, Renault has been most concerned about solving repeated reliability problems with its turbo V6 unit.
"For the third race in a row we have not experienced any reliability worries," said Cyril Abiteboul, Renault's F1 chief, after Canada.
In Canada, the latest specification of the engine was fitted to Max Verstappen's Toro Rosso, costing him a penalty to add on top of his Monaco crash demotion.
It was reliable, but the Dutchman is quoted by De Telegraaf as saying it was still significantly down on power.
"Austria will be another difficult race," he predicted.
But more power is coming, Abiteboul says. With reliability seemingly now under control, "We can move our attention to performance".
Indeed, Renault has more in-season performance 'tokens' in its pocket than any other manufacturer.
Ferrari and Honda spent their first tokens ahead of Canada, Mercedes improved the most during the winter period, while Renault still has 12 tokens to deploy.
The stakes are high, the Spanish daily El Mundo Deportivo claims.
"There is no future for Renault in F1 if we cannot develop a competitive engine," Abiteboul reportedly warned.