Talks for Mandzukic to join United began when the swap deal was agreed in principle for Lukaku to head to Juventus in exchange for Paulo Dybala.
However, United ended their interest in Dybala, the Argentina forward, due to his hesitation over a move to Old Trafford and his wage demands.
In the subsequent days they turned their attention to Mandzukic, but a move for the former Bayern Munich striker has now been called off.
Mandzukic scored 10 goals in 33 appearances across all competitions for Juve last season. During his four years in Turin he has won Serie A four times, the Coppa Italia three times and the Italian Super Cup once.
At Bayern Munich he won the Bundesliga twice as well as the Champions League, UEFA Super Cup and FIFA Club World Cup in 2013 while he also lifted the Spanish Super Cup during a year-long stint at Atletico Madrid.