Andrea Dovizioso said he felt instantly comfortable on his first day riding for the works MotoGP Ducati team.
The 26-year-old Italian secured a switch from Tech 3 to Ducati in August, having been eager to recapture a factory seat following his three-year spell at Honda.
He was one of the first riders out in the morning of post-season testing and Valencia, and consequently managed four laps on slick tyres before the rain fell.
While he therefore finished near the top of the timesheets, Dovizioso said it was the atmosphere of the team and his speed in the wet which had helped him settle so quickly.
"I'm happy after my first day, mainly because I have a good feeling with my crew and I had a good lap time in the wet, even compared to the wet times over the weekend," he said.
"The conditions weren't ideal for a debut on a new motorcycle, but anyway, it was important for me to do some kilometres on the bike.
"The Ducati is known for working well in the wet, and I can confirm that, but obviously we have to try it in the dry.
"Unfortunately, it looks like the weather tomorrow will be like today."
2013 team-mate Nicky Hayden, the fastest rider in the wet, said he had been able to test a variety of settings and also a new frame that Valentino Rossi had been able to trial during the 2012 season.
"I was mainly testing some shock settings and some things that we didn't get a chance to try during the weekend because of the changing conditions," Hayden explained.
"I also tried a different frame that Valentino had tried, and that I wanted to use in the wet.
"Obviously, dry weather would have been better, but it's never a bad thing to do some laps."
While Dovizioso scored six podiums with Tech 3 this year, Hayden and Rossi have collectively finished on the rostrum four times in the past two years.