Manor are "nowhere near quick enough" yet, according to racing director Dave Ryan, with the Dinnington-based outfit once again finding itself fighting at the back of the grid over the final few places.
Although the team has improved considerably compared to last year, partly in thanks to a Mercedes engine deal, they remain some way off the midfield pace and have yet to come close to escaping Q1 in qualifying.
"There is no doubt that this year's car is a massive step on last year's. But we are still nowhere near quick enough," Ryan told Reuters on Thursday.
According to the former McLaren engineer, Manor needs to find another big performance leap before they're satisfied.
"This year we're definitely able to be competitive with some of the cars around us and the performance gap we had to find to do that was massive.
"But we need the same improvement again," he added. "It's not one area in particular, it's everywhere."
However Ryan admits that step might not come for a few years, but insists their target for 2016 is to beat Sauber and claim a top ten finish in the championship standings.
"We clearly desire to be a really solid midfield team, but we also know that's a long game. We are not going to get there this year or next year. It might take four or five years.
"The way we look at it is they [Sauber] are just another team we've got to try and beat. It just happens to be Sauber next door to us and to some people they are the obvious target.
"I think we'd be very disappointed if we didn't finish 10th, that's for sure."
