Earlier this month Kubica covered 115 laps of the Valencia circuit in a 2012 Lotus F1 car.
The test, his first F1 outing since he suffered severe arm injuries in a rally crash in 2011, has raised questions about whether Kubica could have a future in F1.
“I had no doubt on his pace, ever, at all,” Renault’s trackside operations director Alan Permane told Poland’s Eleven Sports.
“I did not know, I don’t think he knew, whether he would be able to drive physically… and, more than that, be able to drive a lot.
“He’s driven some things. He’s driven simulators, he’s driven a GP3 car earlier this year in preparation for this, but we didn’t really know what his limitations would be. And, honestly, it went very well.
“He was quick. He did some long runs, he did some short runs, he did qualifying, we did race simulations and it all went very well.”
Asked whether Kubica had the pace to return to F1, Permane replied: “From what I’ve seen from the statistics, from the data, the pace is there. That’s for sure.”
But while the Polish driver may have the pace, Permane warned that the injuries he suffered back in 2011 may prevent him from being competitive at all tracks.
“On that Tuesday in Valencia he did a fantastic job,” he added. “However, there are many other circuits, and whether he has physical limitations on those, only he knows at the moment.
“If it needs to go any further, that would be the next step.”