Cuquerella was impressed with the performance of his former oufit in pre-season tetsing in Barcelona but like many, insists that the real picture will only begin to emerge when the cars hit the Albert park track.
"What is clear is that they have made a significant step in quality," he said.
"Whether it is enough to compete with or beat Mercedes, I still don't know. But I do know that they will not be as far away as they were at this point last year."
As a former insider, Cuquerella's knowledge and opinion is obviously valued. In his view, Ferrari's improvement has come on the back of "a great investment in development".
"We are talking about an injection of hundreds of millions of euros in tools that allow the testing of most parts of the car," he revealed.
"Ferrari realised this is the deficit they had to Mercedes.
"The results of the winter were strong enough for me to think that they will do well, although I dare not quantify that improvement.
"They may be four tenths behind or two tenths ahead, but at the very least, Ferrari is serious now," said Cuquerella.