So, with Dr Helmut Marko fearing a chassis crack, Red Bull reverted as a precaution to its winter testing monocoque for Vettel to drive in Spain and beyond.
Although grappling with nightmarish reliability for most of the weekend, Vettel ultimately scythed through the field in the race, declaring afterwards: "I feel like I have a car in my hands again."
Asked by Germany's Auto Motor und Sport if he thinks the chassis change was key, Vettel agreed: "I do think it made a difference.
"At least the question mark went away," he added, referring to the uncertain handling of the car he experienced in 2014 until Barcelona.
"As for the pace, it was reasonable," said Vettel.
While happy with the Adrian Newey-penned RB10 overall, Red Bull is pushing engine supplier Renault to make further improvements.
In Spain, the team benefitted from a new blend of fuel supplied by Total.
"In the car itself you don't feel more power," said Vettel, "but we were not as vulnerable on the straight as usual, so I do think it gave us a bit."
But for the moment, he acknowledged that Mercedes is a long way ahead.
"They have a phenomenal engine, two very good drivers, a very good car, and a very good team, they're doing a good job so it would be wrong to complain and moan about how dominant they are.
"They worked better than everyone else in the winter and deserve to be in that position," Vettel added.