The Silver Arrows had predominantly focused on longer runs during testing, more so than faster speed. But the Finn is hopeful that the issues found with handling will be fixed sooner rather than later.
Bottas said at a promotional event in Turin: "We have work to do, but it's a good feeling in the sense that it feels like there is potential.
"We do need to make improvements, we were struggling a bit over the week to find a good balance for all the corners.
"There were some corners that were good, some corners where we would have balance issues and others where we would have massive balance issues.
"We were getting to a much better state at the end of the week," he added, "but some of the handling issues can only be sorted with some upgrades. We're hoping to fix those hopefully soon."
Lewis Hamilton also expressed that he felt the team has work to do, saying: “At the moment we are behind.
"So, we don't approach the first race currently at all relaxed, not that we ever do. We still have a lot of work to do.
"This is going to be the hardest year yet, but I feel I have the best group of people behind to climb that mountain together.
"We are going to face our toughest challenge but I feel like I have the right soldiers behind me.”