Team boss Franz Tost said during the launch of the new STR8 that the Faenza-based squad was aiming for sixth this year after a disappointing 2012 in which the squad could only score 26 points on its way to ninth position.
Key reckons that sixth place is an ambitious target given the resources Toro Rosso has, but that it can be achievable if the team has taken the step forward it hopes for.
"I think that what I've seen in the team is that there are two parts to it," said Key, who joined Toro Rosso from Sauber last year.
"One is the ambition to do it; I don't think anyone was satisfied with P9 in the constructors.
"Secondly, I think the size of the team and the resources we have - and [we] are building - is a big step obviously, and it's a big ask.
"But if we can put ourselves in the mix with the guys who were ahead of us last year, then there's no reason why you couldn't challenge for that position.
"So I think it's possible and the belief and the will are there within the team to achieve.
"It's a great target to have."
Key also admitted the regulation changes that come into play next year are a big challenge for teams like Toro Rosso.
"That's the game everyone has to figure out," he said.
"There will be different splits and people will do it differently depending on the structure of their team and all sorts of other factors, I think, so that's a little bit of a game that needs to be played.
"We have a long season at the end of the year with all the flyaways that represent a chunk of the season when it's difficult to update the car in a big way, so there are all sorts of considerations there.
"It will be a split, and I guess depending on how the teams have worked so far on 2014 will to a certain extent determine that split."