Paul di Resta described his shock return to Formula One on Saturday as "like being thrown off a cliff", after receiving a late call-up to replace Felipe Massa ahead of qualifying at the Hungarian Grand Prix.
Di Resta, who last competed in a grand prix in 2013, was unexpectedly promoted from his role as Williams' reserve driver when Massa withdrew from the race weekend due to illness.
The Briton went on to qualify 19th, only three quarters of a second behind team-mate Lance Stroll and ahead of Sauber's Marcus Ericsson in an admirable performance for someone unfamiliar with the much-changed 2017 cars.
"I'm not going to lie, I was scared, nervous, anxious," Di Resta was quoted as saying by Formula One's official website.
"I've not driven one of these cars for three and a half years, apart from 10 laps I did in a 2014 car, and then you get thrown into qualifying which is the deepest of the deep, I think.
"It's like being thrown off a cliff and seeing how you can fight for survival."
Massa's withdrawal came as a shock to Di Resta, who had been expecting to fulfil his usual role as a broadcaster this weekend.
"I was ironing my shirt at 11 o'clock this morning preparing to be presenting on TV," he added.
"But honestly, I quickly felt quite comfortable in the car. There was nothing that took me by surprise, it's just the more laps you can do, the better it is.
"Honestly, I didn't expect to be so close straight away. I've been here a year and a half waiting for this, so it's a good job I've been attending all the meetings and paying attention!"
Williams' chief technical officer, Paddy Lowe, said: "It was the first time in my experience, having to swap a driver out during a race weekend. First of all, I'm very sorry for Felipe that he's not well enough to compete.
"Paul has been our reserve driver for a year and a half, and he probably realistically never expected to get called up. However, he was ready to go the moment we took the decision and it was very brave of him to go out for his first time in the 2017 generation of F1 cars, along with the new tyres and aero package, to be thrown straight into a competitive session.
"He's got to be my driver of the day to achieve what he did."