Laurence Edmondson F1 Editor 2 Minute Read

BAKU, Azerbaijan -- After Sebastian Vettel took his third pole position in a row on Saturday, Mercedes has revealed it believes Ferrari holds a small engine advantage this year.

Mercedes' power unit has been the class of the field ever since the current turbo-hybrid regulations were introduced in 2014, but Ferrari has shown impressive straight-line speed during qualifying sessions this season. Based on GPS traces, which teams use to analyse the ultimate power of rival engines, Mercedes believes Ferrari now holds the edge in terms of outright engine performance.

"In our analysis it's Ferrari that has a tiny edge over us and is a little bit in front," team principal Toto Wolff said. "Then it's us and then Renault and then Honda. We are super happy with the engine and how the engine went here."

Ferrari has secured the last three pole positions in F1. Dan Istitene/Getty Images

In Azerbaijan this weekend Mercedes' customer teams, Williams and Force India, also enjoyed a strong showing in qualifying, leading some to conclude that Mercedes power is making the difference on Baku's long straights. But Wolff believes a good lap in Baku requires more than just a powerful engine and points to the twisty middle sector as an area that is key to a good lap time

"The power unit works very well here, and undoubtedly it's one of the factors, but there is a 40-second middle sector too. That is tremendously important.

"I would say it's a combination of power unit and mechanical grip, less so high-speed downforce. So clearly you could say if a team performs well in those areas they are going to be looking better."