Ferrari had been the 2024 season's second-best team so far, but didn't live up to those expectations at last weekend's Shanghai event.
Having had at least one driver on the podium across the first four races, Charles Leclerc and Carlos Sainz only qualified sixth and seventh respectively, six tenths off Max Verstappen.
The pair managed to move ahead of Mercedes' George Russell and Aston Martin man Fernando Alonso to finish fourth and fifth, but still fell well short of challenging McLaren's Lando Norris, who convincingly grabbed second.
Team principal Vasseur said his team "made too many mistakes" trying to optimise its package for the tricky Shanghai circuit and its unusual tarmac coating, which led to being behind the curve in qualifying.
"I think it's really a matter of putting everything together," Vasseur explained. "We didn't have a clean weekend on our side, but we made collectively too many mistakes.
"In this group, if you don't do the perfect job you won't be in front. We have a pack with six or seven cars in one tenth in qualifying. That means that due to details you can move from hero to zero."
Both Ferraris initially lost positions to Russell - and briefly Haas' Nico Hulkenberg - at the start as they struggled for grip, which made their recovery harder than it needed to be.
A mid-race safety car further complicated matters for Sainz as he had already made his one pitstop for hard tyres, giving him a tyre-life disadvantage against the cars around him.
But Vasseur pointed out both Ferraris struggled more on the hard compound than on the mediums they had started the race on, which is an area to investigate.
"I think if we lose something today, it's more on the last stint. Carlos was a bit unlucky with the timing of the pitstop, because he pitted three or four laps before the safety car," the Frenchman said.
"He was a bit scared to do a very long stint with the last set of hard and he was a bit conservative at the beginning, but he did very well to manage the long stint.
"We were a bit less performant on the hard than on the medium. We were in a good position at the end of the stint of medium, but we lost ground on the hard."
Shanghai's tricky surface condition, paired to the sprint format's limited practice time, may have tripped Ferrari up, but Vasseur didn't want to call in excuses.
"It's more a matter of extracting the best of what we have, and we didn't do the job this weekend on this," he admitted.
"It was very difficult to understand the tarmac, also due to the format. This can make a difference at the end because we are speaking about one tenth, we are not speaking about half a second.
"But this cannot be an excuse. It's the same for everybody and some teams managed it better than others. We have to understand if we can do a better job with the preparation."
Additional reporting by Erwin Jaeggi
