Nico Rosberg has singled out Williams as a potential threat as he chases a hat-trick of Austrian grand prix wins this weekend.
And the championship leader is not the only one expecting the Grove team to shine at the Red Bull Ring, despite the fact Ferrari and Red Bull have been more consistent challengers to Mercedes this year.
"Traditionally, Williams are strong in Austria as they have the highest speeds on the long straight," Marc Surer, a former F1 driver turned pundit for German broadcaster Sky, said.
Rosberg had earlier told Bild newspaper: "I am especially looking at Williams. They always put us under pressure there."
However, team boss Toto Wolff thinks Mercedes’ actual challenge in Spielberg will come from the usual suspects.
"For me, the challengers are - in order - Ferrari, Red Bull, Williams and Force India," he told the Italian newspaper Corriere della Sera.
But he also insisted that Mercedes is being pushed to its limits in 2016.
Asked if F1 is witnessing the gradual end of Mercedes’ era domination, Wolff answered: "Each era always ends - even the Roman Empire experienced it."