Lorenzetti joined Rosario Central youth squad in 1994. He made his professional debut for Rosario Central of the Primera Division Argentina on September 28, 2003. The coach at the time was Miguel Russo. Lorenzetti made his first start on February 22, 2004 against Boca Juniors. He also participated in Copa Libertadores 2004.
In 2006, he was loaned to Chilean club Coquimbo Unido. The team made it to the playoffs and Lorenzetti made 4 goals and twelve assist that season.
In 2007, Lorenzetti was loaned again to Chilean club U. de Concepción with an option to buy the player at the end of the year. He again made the Chilean playoffs. In the first round of the playoffs, U. de Concepción upset Universidad Católica. In the second leg of the semifinal against Audax Italiano, the number one seed, U. de Concepción was on the verge of elimination when Lorenzetti scored an amazing goal to qualify U. de Concepción to the final against Colo-Colo.
In 2008, U. de Concepción picked up the option on Lorenzetti and bought the rights to the player.