Paul di Resta claimed he was relatively satisfied with how his one-off return went at the Hungarian Grand Prix, after being called up before qualifying to replace an ill Felipe Massa.
The Scottish reserve driver, who last competed with Force India in 2013, had not driven the 2017 Williams before Q1 on Saturday but would beat Marcus Ericsson to start 19th and was only seven tenths slower than full-time racer Lance Stroll.
In the race, he would jump the second Sauber of Pascal Wehrlein initially but would fall behind during the pit-stop phase to run at the bottom of the field before an oil leak forced him into retirement 10 laps from the end.
Revealing his feelings at being back in the car, the 31-year-old, who beat Sebastian Vettel at the same team in Formula 3, said: “It was obviously very exciting but it was very difficult as well to jump straight in the car with no experience of the different tyre compounds or running on high fuel.
"I wasn't sure what to expect so I went in with an open mind."
Asked what his main concerns were as a result of having no experience of the faster 2017 cars other than on the simulator, he added: “You have to be very aware of the space around you and how much downforce you lose when there's traffic around you. So I was cautious and just wanted to keep my nose clean.
"Unbelievable job, honestly," said the Austrian on Di Resta's performance, as he improved by 2.4 seconds in five flying laps. "To be put in this car in qualifying, never having driven it, having done a handful of laps in a 2014 car to give some comparison for Lance, and driving a touring car regularly.
"He's been catapulted into an F1 car and is within seven-tenths of his teammate and doesn't look ridiculous at all, is a major achievement. I'm really happy for Paul because that was in my opinion against all odds."
"There's no secret I want to be in an F1 car but at the very least I hope I've shown I'm a reliable reserve driver kicking around the paddock," he said.
"I tried to approach it in the most professional way I could and gain a lot [of experience] rather than throw away something that wasn't there [in terms of a potential result]."
