Mercedes have now solved their early-season tyre problems, according to Pirelli chief Paul Hembery.
The German team bounced back from their podium absence at Monaco to dominate in Canada two weeks ago.
"The hard work paid off," Hembery told Germany's Auto Bild.
"What they did between Monaco and Canada was impressive - a dramatic step."
He also played down recent speculation that Mercedes's struggle was amplified by an alleged advantage gained by Sebastian Vettel over the winter, as the Ferrari driver participated heavily in Pirelli's 2017 test programme.
"We would have liked more top drivers as committed to work as Sebastian was [to join him]," Hembery said.
"He gave us important feedback from morning to night, pushing us in the direction the drivers wanted, and we have to thank him because it makes a difference whether an inexperienced driver or one of the best tests tyres."
However, he thinks that any advantage Vettel got was fleeting.
"If there was an advantage, it was at the very first winter test this year," said Hembery.
The championship continues on Sunday with the Azerbaijan Grand Prix.
