Manchester United have already made significant progress in the transfer window.

Victor Lindelof and Romelu Lukaku will make a huge difference to Jose Mourinho's XI, as he now has a solid defensive partner for Eric Bailly and a successor to Zlatan Ibrahimovic.

So far, so good. Mourinho is nowhere near finished, though.

United's attentions are already turning to a holding midfielder.

Michael Carrick may have just been made club captain, but the 35-year-old can't go on forever.

The departures of Bastian Schweinsteiger and Morgan Schneiderlin last season have made it all the more crucial that the Red Devils bring in reinforcements.

It's no secret that Eric Dier is the man at the top of their wishlist.

The versatile Tottenham man spent the end of the last campaign on the right side of a back three, while he can also play at centre-back.

Although he has lost his central midfield place to Victor Waynama, it's there that United would want him to operate.

"Hard to turn down"

An interview from 2010 has been doing the rounds in which a then 16-year-old Dier told the BBC that United would be "very hard to turn down".

However, this might not be the match made in heaven it appears to be.

The England international made those comments as a teenager when he was yet to establish himself at Sporting Lisbon, and he may well feel differently now he is flourishing under Mauricio Pochettino.

Regardless, Daniel Levy has made it clear that the 23-year-old isn't for sale, even if United were to offer a healthy £50million.

So, it seems Dier won't be continuing his Portuguese football education under Mourinho.

Who else is on United's list?

It poses the question of where United go next. Nemanja Matic and Fabinho are the other names being regularly linked, but the Daily Mail's latest report will have fans particularly excited.

The newspaper suggest United will rival Chelsea for Roma's Radja Nainggolan.

The dynamic box-to-box Belgian international has been attracting interest from Europe's elite clubs for some time.

Inter Milan are monitoring the 29-year-old too, but Roma are conscious that it would irritate their supporters if they were to sell to another Serie A club.

The Giallorossi's sporting director, Monchi, insisted recently that Nainggolan would stay in the Italian capital as Roma have already lost Mohamed Salah to Liverpool - but the Mail point out that selling him would allow them to reinvest funds in their squad.

"Yes (he will stay)," Monchi recently told asroma.com, per Sky Sports.

"I think we've seen the last of the big departures from our club."

United could end up disappointed again, but it will be a huge relief to Tottenham if they are indeed starting to look elsewhere.

Who would be a better signing - Dier or Nainggolan? Have your say in the comments.