 Complete the following phrase:  Another former player, Giovanni Vavassori, was appointed as head coach of the senior team in 1999, after winning several trophies with the Primavera team during the 1990s. The club also chose to invest in its youth system, spending an estimated 3.5 billion lire per year in 2000, far more than any other provincial club in Italy. As the club often lacked the money to purchase world-class players from abroad, it heavily emphasized youth development since the 1970s. Under the guidance of Vavassori and with the help of homegrown players in the senior team, as well as the return of Caniggia though he would leave at the end of the season, the club achieved promotion to Serie A. Among these players was defender Gianpaolo Bellini, who made his debut under Mutti during the previous season in Serie B; he would spend his entire career at Atalanta retiring in 2016, after 18 years and record a total of 435 appearances, the most of any player for the club. Atalanta started the 200001 season in 