The Argentine forward has displayed a positive attitude since returning to the Stadio Olimpico after a largely unsuccessful loan spell at Inter last season
The Argentine spent last season on loan at Inter but the Nerazzurri ultimately opted against signing the forward on a permanent basis.
Lazio's initial plan was to then find a new home for Zarate but, according to Corriere dello Sport, the 25-year-old has now convinced Petkovic of his worth by committing himself fully to the Biancocelesti's pre-season training programme.
Indeed, club officials now believe that the former Birmingham City man could now prove to be Lazio's most important 'signing' of the summer.
Zarate initially joined the Roman outfit on loan from Al Sadd in 2008 but he sealed a permanent switch the following summer.