Toselli is best known for beating Cláudio Taffarel‘s clean sheet record of 484 minutes during 2007 FIFA U-20 World Cup of Canada, surpassing him by eight minutes and completing 492 minutes in total, helping Chilean youth squad to a third-place finish. In 2009, he was a member of Ivo Basay‘s 23-man squad who won the Toulon Tournament, a tournament that Cristopher lost in 2008 against Italy under Marcelo Bielsa as coach.
Born in Antofagasta, Toselli joined Universidad Católica youth ranks in 2001, being promoted to first-team by the coach Jorge Pellicer in 2006 for the Torneo Apertura, due to the departure of second-choice keeper Rainer Wirth to Deportes Temuco. The following year, after a notable performance in the FIFA U-20 World Cup, he made his club debut on 25 November, during a 3–0 home win to Coquimbo Unido played at San Carlos. The next season, he was challenging the goal with record-man José María Buljubasich, becoming the first-choice keeper, after their mistakes and its departure to Olimpia.
When he played the 2009 Toulon Tournament final against France, that Chile won 1–0 to Les Blues, Toselli suffered a strong injury of six months, that caused indignation Católica’s coach Marco Antonio Figueroa for provide him to a tournament and take risk, because he was Figueroa’s starter keeper. During his recovery time, second-choice keeper Paulo Garcés broke into first team, therefore relegated him to the bench.
On 11 May 2011, he recovered his titularity under orders of Juan Antonio Pizzi after a terrible mistake of Garcés in a Copa Libertadores quarterfinals match against Peñarol at Montevideo, where inexplicably dropped the ball, which Alejandro Martinuccio take the opportunity for score the definitive 2–0 in the 90th minute. After losing against Universidad de Chile the playoffs finals of the Torneo Apertura, was installed again as starter keeper with the new coach Mario Lepe, after the departures of Pizzi and Garcés. On 16 November, Toselli won the Copa Chile final to Magallanes, being that his second title at Católica, that qualified his team 2012 Copa Sudamericana, which Los Cruzados were eliminated on semifinals against Brazilian side São Paulo after two draws, where Toselli had very well performances.