United are presently preparing for their third campaign under the Portuguese, but Mourinho has in recent times suggested that he is growing frustrated with the club’s efforts in the transfer market.
Mourinho has also failed to last longer than three years in his last three roles. According to The Sun, the Premier League giants have already begun putting contingency plans in place.
The report claims that Zidane would become United’s top target should Mourinho leave United, with the 46-year-old available after departing Real Madrid earlier this summer.
Zidane is presently taking a break after his trophy-laden spell at the Bernabeu, but taking over at United in the future would possibly appeal to the Frenchman.