Naydenov won the top Bulgarian league, the A PFG, 8 times (all with CSKA), as well as the Bulgarian Cup, 3 times (all with CSKA).
He was respected for his incredible work ethic and his determination during training and matches alike.
For the Bulgaria national football team Naydenov featured in 51 games and won a bronze medal at the 1956 Summer Olympics.
Even after he had retired from competing he still remained one of the fittest players in Bulgaria and this made his death all the more mysterious.
He died in Damascus, Syria and initial reports claimed he had suffered a heart attack although members of his family and people close to him suspected he had been poisoned.