The Lotus reserve driver was told only 15 minutes before the session was due to get underway that he would be standing in for Kimi Raikkonen, who was too unwell to drive.
He completed fewer laps than anybody else during the morning - 16 – and set the ninth fastest time. He was not helped when his E21 was halted by a minor technical glitch that also caused a red flag.
The Italian then handed the car over to Romain Grosjean, who had returned from Paris during the morning, for the remainder of the day.
"It was nice to drive and to do some laps, even if really I only did seven laps that were not coming into the box," he said. "It's a good thing to get some time in the car.
"Here at Lotus the drivers will be fighting for podiums, so I should be strong enough to fight for the top five or six.
"I think right now, if Kimi could finish third in Australia, then I could finish sixth.
"I would like to be strong enough to fight for victories in Formula 1 and I don't see why I can't be fast enough. When I am there, I'm sure I'll get my opportunity."
Valsecchi admitted that his preparation for taking over Raikkonen's car had been far from ideal.
"This morning I found out I was driving at 08:45, which was great," he said.
"The problem is that all my stuff is in Australia, so I used all of Raikkonen's equipment; seat, overalls, shoes... Everything except the underwear, which wasn't there.
"It wasn't so much of a problem. When they told me 'you have to use Raikkonen's seat', I just thought 'it's the seat of an ex-world champion, so it will be fast'."
Valsecchi confirmed that his next scheduled outing for the team would be in a two-year-old Renault, equipped with 2013-spec tyres and engine.
The test is due to take place at Paul Ricard on April 1-3.
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