Mika Salo - a former Ferrari, Sauber and Toyota race driver - has admitted his surprise at how F1 technology has moved on since he retired in 2002.
The now 45-year-old Finn got back at the wheel of a modern grand prix machine last weekend at Suzuka, during the Ferrari Racing Days event.
"The power came as no surprise," he told the broadcaster MTV3, "but the grip was quite unbelievable.
"It was almost contrary to the laws of nature, how hard you could be pushing on sixth or seventh gear in a corner.
"I would have needed many more days to really get back on terms with it," said Salo. "I have to admit there is no way I could do a race right now.
"Secondly, my fitness really is not enough — I have such a sore neck and hands now that I could barely carry my bag at the airport," he added.