Manchester United have tabled a bid for Borussia Dortmund defender Mats Hummels. The Daily Express says Hummels is a longstanding target for Louis van Gaal as he looks to address his side's defensive shortcomings.

And while Borussia Dortmund have insisted that the 26-year-old is not for sale, that hasn't deterred United from making their interest known.

Indeed, reports in Italy suggest that United have lodged an opening bid with Dortmund over a prospective January transfer.

Hummels has previously been valued at anywhere between £30m and £50m, and while it is not currently known where United's opening bid fell within that range, a sizeable fee is surely necessary if the Old Trafford outfit have any chance of pulling off a deal.