The Croatia international was believed to have been close to signing for United last summer, but the move didn't materialise.
United were in pursuit of Mandzukic's team-mate Paulo Dybala and it was thought that a double deal might be done.
However, any agreement depended on Romelu Lukaku travelling in the other direction - but Lukaku had his heart set on Inter Milan.
Dybala, meanwhile, had no intention of leaving Juventus and was keen to prove himself to new coach Maurizio Sarri.
Mandzukic ended up caught in the middle of a transfer whirlwind, and despite United reigniting interest late on in the window, a deal couldn't be done.
Their 17-year-old prodigy Mason Greenwood is emerging, but it's thought that Solskjaer doesn't want him to be relied upon too heavily at his age.
But the 33-year-old is now out of favour in Turin, having been omitted from their Champions League squad this year.
