The La Liga giants have been chasing Pogba all summer but are yet to agree a deal on the eve of the Premier League's transfer deadline on Thursday.
And if Madrid are unable to prise the midfielder away from Old Trafford, they will turn their attention to Neymar.
The Brazil international is desperate to leave PSG this summer, while the French champions are also willing to let him go for the right price.
However, it is unclear whether Madrid would be able to meet PSG's valuation of a player they signed for £198m in 2017.
The European transfer window does not close until the end of August, giving Zinedine Zidane's side more than three weeks to try and get a deal over the line.
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