Former Germany and Bayern Munich star Effenberg said he had no idea why the Bundesliga giants sold Mandzukic in 2014, while revealing he preferred the forward to Brazil and Paris Saint-Germain star Neymar.
"I never understood why Bayern sold him," he wrote for T-Online .
"Mandzukic is one of three three best strikers in the world for me. He is working for the team and also scored the goal against England.
"If he were not so old, he would have a market value of €200m. I would prefer him 10 times better than a Neymar."
Mandzukic has scored at least 10 goals in his past seven seasons, going across the Bundesliga, La Liga and Serie A, and will have the chance to add a World Cup title to his list of honours with a win on Sunday against France.