Michael Schumacher admitted his return to F1 on Monday reminded him of when he started out in the sport in 1991.
The seven-time world champion returned to the sport from which he retired more than three years ago at the wheel of the Mercedes W01, setting third fastest time of the day.
"In a way it is like 1991, honestly," Schumacher said. "When I came into F1 I was shocked on the first lap and extremely excited on the second lap and further laps. And it is exactly the same today.
"I feel like a young boy that has a toy in his hands and enjoys himself."
Schumacher admitted it was strange to not be in a Ferrari, after spending 13 years with the team prior to his Mercedes switch.
"Naturally I suddenly see my old car on the track and not siting in it, it is a strange sensation," he said. "But it was good to see my brother [Massa] on the track, in the car and I enjoyed to see my friends down at Ferrari this week."
Schumacher also pronounced himself pleased with his day's work.
"I think we have done a very good job. The guys did a superb job out there, being out there making a few control checks and making the car reliable. We did more than 80 laps, and for the first day that is a superb job."