Mandzukic, the Croatia international who helped knock England out the 2018 World Cup, was seen as the ideal replacement for Romelu Lukaku, who departed Old Trafford for Inter Milan.
Mario Melchiot on the situation at Manchester United
The 33-year-old has failed to make a single appearance for Juve this season, only appearing on the bench in three of four Serie A games played so far.
He is expected to leave the club either in January or next summer, and Tuttosport say Mandzukic will reject a big-money offer from Qatar and assess his options at the start of 2020.
The forward is said to prefer a move to the Premier League, and the report claims United are still keen on Mandzukic having been interested in signing him in July.