Toro Rosso say they think Alguersuari will take three races to acclimatise to F1
Toro Rosso have announced that Jaime Alguersuari will drive for the team, taking the place of the sacked Sebastien Bourdais.
The Spaniard, 19, will become the youngest driver to take part in a Grand Prix when he races for the Italian outfit in Hungary this weekend.
The British Formula Three champion has been picked from Toro Rosso's young driver programme by boss Franz Tost.
Toro Rosso let French driver Bourdais go after two seasons with the team.
Bourdais scored six points in 27 grands prix for Toro Rosso, but is now threatening legal action against them for what he considers a 'breach in his contractual duties'.
I do not expect anything from him for at least his first three races
Toro Rosso boss Franz Tost
Reports say that five-time world rally champion Sebastian Loeb could drive for Toro Rosso in the last Formula 1 race of the season in Abu Dhabi.
Barcelona-born Alguersuari will join team-mate Sebastien Buemi, who until the Spaniard's arrival was the the only rookie driver racing in F1 this season.
"I am aware that I'm facing a very tough challenge, because coming into Formula 1 is never easy," said Alguersuari.
"Coming into Formula 1 in the middle of the season is even harder and doing so without any testing is really difficult.
"But already I feel I am getting great support from the team, who have quite a reputation for looking after rookie drivers."
Tost said Alguersuari was chosen to replace Bourdais because he was considered the "most mature" prospect in the young driver programme.
He added: "I do not expect anything from him for at least his first three races, during which he has to get used to the car, the team and to the F1 environment."
Alguersuari takes over from New Zealander Mike Thackwell as the youngest driver to start a GP weekend.
Thackwell took part in the Canadian GP in 1980 at the age of 19 years and 183 days, but was not classified as a race-starter because he did not take line up when it was restarted after a first-lap crash.
Alguersuari will be 19 years and 125 days if he starts Sunday's Hungarian GP.