Real Sociedad coach have replaced departing boss Philippe Montanier with his 34-year-old former assistant Jagoba Arraste.
Vizcaya-born Arrasate was made Montanier's assistant at the start of the 2012-13 season, having previously worked impressively with the Basque club's underage sides.
The pair guided La Real to surprise Champions League qualification last season, but Montanier has now left to take charge of ambitious Ligue 1 side Rennes next term. The new man will be presented to reporters in San Sebastian on Saturday morning.
Aperribay admitted that once Montanier turned down a new contract, the Basque club had first approached current Newell's Old Boys and former Paraguay coach Gerardo Tata Martino, then decided the best course was to promote the highly rated coach from within.
"Jagoba Arrasate will coach la Real Sociedad next season, he is the choice to continue along the strategic line marked out for some years," Aperribay side.
"When Montanier closed the door on continuing we thought of two names - Tata Martino and Jagoba Arrasate. We think we are going to start the next season without any doubts and with the perfect knowledge of what we have."
Most of Sociedad's current first team - including starlets Asier Illarramendi, Antoine Griezmann and Inigo Martinez - have worked at the club's Zubieta training facility under former lower division striker Arrasate at youth level, and Aperribay said it was not too early for the young tactician to get the top job at Anoeta.
"This is not a gamble, we want to continue along the sporting line we have marked out," the president said. "It is the moment for [Arrasate] to assume this responsibility. Jagoba knows the internal workings at La Real absolutely, he has all the characteristics we were looking for. This is not an experiment - an experiment would be to bring in a coach from outside who did not know us."
Despite the extra requirements of possible Champions League group stage football next season, La Real are not expected to spend big this summer.
With their promising youngsters tied to long term contracts, no more than a few tweaks are reportedly planned. Carlos Vela's agent has said the Mexican attacker will stay despite Arsenal's buy-back option, while young Barcelona defender Marc Muniesa has reportedly agreed to join on a free.
"Our intention is that nobody leaves and from here on we can reinforce with one or two new signings," Aperribay said. "Our economic situation is still tight enough. We need to keep consolidating and building with our young players from here."
Lille manager Rudi Garcia, Mainz coach Thomas Tuchel and San Sebastian native Unai Emery - currently at Sevilla - had all featured in speculation about Montanier's replacement in recent weeks, while Laurent Blanc was heavily rumoured as a surprise candidate on Friday afternoon. Aperribay said none of these had been approached.
La Real's fourth place finish last season earned them a place in the qualifying around - however their low seeding means Arrasate's first game as a senior club coach could be against Arsenal, Milan, Lyon, Schalke or Zenit Saint Petersburg.