In 2018, Ferrari had the more powerful power unit for the first half of the season, looking as if they would give Mercedes a real challenge for the constructors' title.
However, the Silver Arrows went onto dominate the second half of the season and were crowned world champions once again.
After pre-season testing in Barcelona took place last week - Bottas believes it is a "fact" that Scuderia hold the upper hand at this point in time.
"Ferrari seems to be ahead of us at the moment. That's a fact," Bottas claimed.
But Bottas did admit that things could be different come the first race in Melbourne in March, with his side looking at Ferrari's front wing design for inspiration.
"The tyre window is very small and the balance is on a knife's edge," Bottas, explaining Mercedes' problem. "We have problems in some corners and bigger problems in some others.
"But it does not feel like something is fundamentally wrong with the car."
Bottas will be aiming to win a race this season after a winless 2018 for the Finn has put him under immense pressure, with Esteban Ocon waiting in the ranks.