Mercedes ended pre-season testing with the fastest time and more laps completed than any other team, prompting Ferrari chief Mattia Binotto to declare his team was behind on pace.
Vettel and teammate Charles Leclerc supported Binotto's assessment, but Mercedes pace-setter Valtteri Bottas was unwilling to read too much into the comments, saying teams play "weird games" in winter.
Vettel reported that his Ferrari car felt "too draggy" through testing, having lapped a second off Bottas' benchmark time.
Asked if he felt worried by what he'd seen from Mercedes, Vettel replied: "It just looks as if Mercedes is more at ease.
"Not just for the one lap, which is what people look at, but just in general, also the [long] runs.
"I think we also had some runs that were better, some runs that wer