The two clubs are set to go head-to-head in the Champions League quarter-final first leg at Old Trafford on Wednesday night.
Xavi won the competition four times with Barça before leaving the Camp Nou to join Qatari club Al Sadd in 2015.
Speaking to The Mirror, the World Cup winner examined the two squads on a position-by-position basis.
Goalkeeper
Barcelona - 9
“I saw Ter Stegen on his first day at the club and I remember that I was impressed with his qualities immediately," he said.
"Since then he has grown into one of the top goalkeepers in the world. He has a lot of experience in playing in the big games, is so professional, and he knows how to handle these big occasions.”
Manchester United - 9
“De Gea is one of the best as well – it's no surprise that Manchester United are so keen to keep him. He is such a quality player – but what we have seen with him is that he so often rises to these big games.
"He has got United results in the past that they have had no right to get. He can make saves so few goalkeepers in the world are capable of – and United are going to need him to be at his best.”
Defence
Barcelona - 8
“This season Barcelona have let in more goals than is normal for them and that will give Manchester United some hope I am sure.
"In games like this you need a leader and a player like Pique need to make sure the rest of the team stay calm and composed. He has won everything and can be that leader.”
Manchester United - 7
“This is not one of the great Manchester United defences – they don’t have that great leader in the middle that they had in so many of their great teams of the past.
"They are going to need to produce one of the great defensive performances of their season if they want any hope of getting a result against Barcelona.”
Midfield
Barcelona - 9
“There is so much experience and such talent in the Barcelona midfield that I am sure they will look to control the midfield in both games.
"Players like Busquets and Rakitic know what it takes to take charge of the midfield in big European games – and I expect them to dominate.”
Manchester United - 8
“So much depends on Pogba. Since the new coach has taken over – he looks a new player – the sort of player Manchester United paid all that money for.
"If they are going to be competitive in midfield he needs to show his physical dominance and it will give the midfield players around him confidence as well.”
Attack
Barcelona - 10
"Messi just keeps getting better and better, he is the best ever and this season is looking as dangerous as ever. When he is like this he is impossible to keep quiet.
"Suarez has a lot of experience of playing Manchester United as well – and getting goals for him in this game would mean a lot to him.”
Manchester United - 9
“This is an area that Manchester United can really cause Barcelona a problem in.
"Lukaku is a big physical threat and then they have then players like Martial and Rashford who have a lot of speed, a lot of quality, and both can get goals.”
Barcelona 36-33 Manchester United
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