The Red Devils are looking to strengthen their defence after 32 goals in their 21 Premier League matches.
And Marca claim United are close to signing the impressive Manolas.
The Greece international has a £30.75million release clause in his contract but it doesn’t become active until the summer.
Manchester United are unwilling to risk missing out on Manolas though and want him to make the switch to Old Trafford this month.
Ole Gunnar Solskjaer’s side have also been credited with interest in Eder Militao.
But Marca suggest Real Madrid are now favourites to sign the Porto defender.
Former United boss Jose Mourinho was critical of the club for not bringing in a centre-back in the summer.
Ed Woodward missed out on a number of targets including Harry Maguire, Toby Alderweireld, Jerome Boateng and Diego Godin.
But it seems United will finally sign a centre-back in Manolas this month.
The 27-year-old talked up playing for a club like the Red Devils in the summer.
Speaking in July, he said: “It’s only natural you want to play for the biggest clubs, like Barcelona, Manchester United, Paris Saint-Germain and Bayern Munich.
“I think I could make the difference anywhere I went, even at Barcelona – although I have never spoken to them.”
United return to Premier League action on Sunday when they take on Tottenham (4.30pm).
Solskjaer is looking to make it six wins on the spin after replacing Mourinho.
Spurs boss Mauricio Pochettino is the favourite to become the permanent United manager in the summer.
But a win for Solskjaer could put him in a good position to make a case for the job.