Fernando Alonso has the "speed, hunger, motivation and experience" to help Aston Martin take the next step but things could get difficult if they do not deliver a fast enough car for the former world champion, team boss Mike Krack said on Tuesday.
"It will be challenging for us," Krack said in an interview with the BBC. "Normally, drivers with this experience, they do not have this desire to win... especially if they have won already.
"Fernando has this unique combination of speed, hunger, motivation and experience. For us, it makes the perfect candidate. The downside could be that if the car we deliver is just not good enough, then we know it gets difficult.
"We think having someone like Fernando is really, really important to make the next step as a team."
Aston Martin have had 11 top-10 finishes this season, with Vettel's sixth place at the Azerbaijan Grand Prix their best result. They are ninth in the 10-team constructors' standings with six races left on the calendar.
"You need to learn to manage champions, which we already did with Sebastian," Krack added. "Because these drivers are very demanding, they are quite difficult to manage.
"I would not even say Sebastian is that difficult to manage if you are transparent, honest and straight. And I think the same goes for Fernando.
"He knows very well when he comes here that we will probably not win the first race together. But he can be assured we give it everything and we will listen to what he has to say."