Esteban Gutierrez was delighted to have made his debut on a grand prix weekend after replacing Sergio Perez in opening practice in India.
The Mexican, who had never driven this year's Sauber on a circuit, took to the wheel of the C31 in the morning session as Perez was unwell.
Perez returned to action in second practice.
Gutierrez completed 29 laps on his way to the 20th quickest time of the session, some 1.4 seconds off team-mate Kamui Kobayashi's time.
The 21-year-old said he really enjoyed the experience.
"It was a great experience to step in for Sergio this morning," said Gutierrez. "For me it was the first time I have been at the wheel of the C31, as I have only done straightline testing so far. Also I didn't know the track before, which made it an even more interesting session.
"Today I really enjoyed seeing from the inside of the cockpit what I had only seen from the outside.
"It was also very interesting to be part of an official Formula 1 event for the first time. It is obviously different to testing and it is challenging to stay focused.
"I think the circuit here is amazing, especially with the chain of fast corners. However, my target was to progress during that session and make sure I brought the car home in one piece."
Gutierrez added that he now felt capable of stepping in at short notice in the future if required.
"Now Sergio will be taking over again but, in case anything should happen, I feel ready to get into the car again," he said.