In January 2006 Petráš joined Saturn Ramenskoe in Russia, where he played 54 matches in 3 years.
After three years in Saturn, Petráš joined ŠK Slovan Bratislava in January 2009.
Peter made his official debut for Levski on 7 March 2010 against Minyor Pernik.
In 2009/2010 season, after couple of bad games and results, Levski however achieved qualifying for UEFA Europa League becoming 3rd in the final ranking.
Petráš has been playing for Slovakia national football team since 2006 He has already made 9 appearances for the side.