Valtteri Bottas is not quick enough to maintain Mercedes' dominance of Formula One, according to Red Bull technical director Helmut Marko.
The Silver Arrows have been the team to beat in recent seasons with Nico Rosberg and Lewis Hamilton winning the last four drivers' titles, and the team crowned top constructor since 2014.
Rosberg will not drive for the team in 2017, however, the German having surprised the F1 world by retiring five days after he won the world championship last season.
His place has been taken by Valtteri Bottas and the Finn impressed with his pace during pre-season testing.
Marko is not convinced by the former Williams driver, though, and believes 2017 could see Red Bull and Ferrari break the Mercedes one-two.
"Barcelona has shown that Bottas cannot go at the speed of Hamilton," he told Red Bull's Servus TV channel.
"Should Mercedes have the same kind of technical dominance, there will not be the same one-two formation again.
"Then, others will be able to place themselves between the Mercedes drivers."