born in elin pelin, sofia province, tonev was raised in cska sofia's youth teams. he made his first team debut in a 3–1 league win over belasitsa petrich on 8 march 2008, coming on as a substitute for chigozie udoji. tonev got his chance in cska's first team after the sale of many players in the summer of 2008. he played in the club's first fixture in the 2008–09 season against litex lovech on 3 august 2008. his team won the game and won the bulgarian supercup for the third time.