Teenager Sancho left Manchester City
to join Borussia Dortmund for £8million in the summer of 2017.
The winger has become a regular in the Dortmund side this season and his form led to a call-up to the senior England squad.
Sancho made his Three Lions debut as a substitute against Croatia in October and shone on his first start against the USA last Thursday.
talkSPORT host Adrian Durham was seriously impressed with the 18-year-old following the 3-0 win over USA.
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It's a gargantuan clanger from Pep Guardiola, let's not dress it up as anything else
Adrian Durham on Man City selling Jadon Sancho
He claims selling Sancho was a massive mistake from City boss Guardiola.
And Durham says Manchester United
should do all they can to 'annoy' their rivals by signing their former player.
'It's a gargantuan clanger from Pep Guardiola
, let's not dress it up as anything else,' Durham said.
'Listen, while he's in the Bundesliga and people are wowing about him and he's getting the odd goal - I've looked at his goals and some of them are deflections, some of them are tap ins.
'He's not doing bad but is he that great? Well we saw on Thursday, this is a confident player on the ball, he's direct when he's on the ball, he has a way of just challenging his opponent, it's something that we need.
'He's another Raheem Sterling waiting to happen isn't he, that's how he plays.
'So there's no doubt, I think in anybody's mind, what did they get for him, £8m, Man City? It's pathetic really.
'It's a massive, massive, monumental error from Pep Guardiola.
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'Man United knocked Liverpool off their perch famously, that was Fergie's quote.
'Man City, the noisy neighbours, have now taken over.
'So United have got to do all they can to annoy Man City and if possible, it's going to be very difficult, overtake them again.
'That will come with time, but how annoying would it be if they sign Sancho?'