The former Croatia international last played for AC Milan in the second half of the 2020/2021 season, failing to score in 10 appearances for the Rosonerri.
Mandzukic also turned out for the likes of Dinamo Zagreb, Wolfsburg, Bayern Munich, Atletico Madrid, Juventus and Al-Duhail.
Mandzukic won two Bundesliga titles and the UEFA Champions League with Bayern Munich while his spell at Juventus brought four Serie A titles and three Coppa Italia trophies.
Mandzukic was a member of the Croatia side that made it to the final of the FIFA World Cup in 2018, scoring three goals in Russia.
He scored two goals in the final, including an own goal as Croatia lost 4-2 to France. In all, he amassed 89 appearances for his country and scored 33 goals.
In a post on Instagram, Mandzukic wrote: “Dear little Mario, while wearing these shoes for the first time, you cannot even imagine what you will feel in the world of football.
“You will score goals on the most important stages, and you will win the biggest trophies with the biggest clubs.
“Proudly represent your country, you will contribute to writing the history of Croatian sport.
“You will be successful because you will have good people around you: teammates, coaches, fans and family members, agents and friends who will always be there for you.
“You will be forever grateful to all of them! Above all, you will be successful because you will always give your all.
“In the end, this is what you will be most proud of. You will sacrifice a lot, but you will know that it was worth it because of all the amazing moments.
“You will recognise when it’s time to retire, to put these shoes in a closet and you will have no regrets. Football will always be part of your life, but you will be looking forward to a new chapter.
“Have fun! Your big Mario. P.S. If you happen to play against England in the World Cup, be ready around the 109th minute.”
