In the 2009–10 season Petrov brought home the silver medal in the novice event at the 2010 Toruń Cup and finished just shy of a medal at Rostelecom Crystal Skate. The following season, Petrov won gold at the 2011 Toruń Cup, his first international gold medal. In the 2011-12 season, he won the novice event at the 2011 NRW Trophy in Dortmund, Germany and finished second in the junior event at Rostelecom Crystal Skate. Making his debut at the 2012 Russian Junior Championships, he finished 12th.